Chapter Four · failure evidence
What Semiconductor Doping & Implantation got wrong, from 51 dissertations
Doping and ion implantation methods frequently fail due to crystal damage, incomplete electrical activation, and unwanted dopant migration during thermal processing. In addition, chemical and environmental interactions can trigger severe carrier mobility degradation, phase separation, or unintended doping. These records come from PhD theses at 15 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Incomplete dopant activation, deep trap formation, and carrier self-compensation
Attempts to modulate carrier conduction often failed because incorporated dopants formed deep midgap trap states or experienced severe self-compensation. In other cases, low electrical activation efficiency, carrier freeze-out under cryogenic conditions, or unintended free carrier generation prevented effective doping control.
Tried and failed
transition metal doping for deep level compensation applied to ferroelectric nitride thin films. Outcome: worse than baseline. Reason: dopant introduction significantly increased leakage current instead of reducing carrier conduction
TOWARD III-NITRIDE BASED FERROELECTRIC HIGH ELECTRON MOBILITY TRANSISTORS · Cornell
Tried and failed
higher-valence cation doping to suppress leakage applied to perovskite oxide thin films. Outcome: worse than baseline. Reason: donor doping introduced additional free carriers rather than compensating defects, significantly reducing electrical resistivity
Cation Site Occupancy and Defect Engineering in Perovskite Heterostructures · MIT
Tried and failed
sol-gel Pechini transition metal co-doping applied to semiconductor photocatalysts. Outcome: no signal. Reason: insufficient suppression of high-valence dopant trap states that quench photoresponse
Tried and failed
alkali metal codoping to suppress trap states applied to transition metal doped perovskite photocatalysts. Outcome: no signal. Reason: failed to suppress midgap trap states and unwanted sub-bandgap optical absorption
Tried and failed
beryllium doping for p-type conductivity applied to gallium nitride epitaxy. Outcome: no signal. Reason: deep acceptor energy levels and self-compensation mechanisms resulted in semi-insulating material rather than p-type conduction
Investigation Of Metal Modulated Epitaxy Grown III-Nitride High-Power Electronic And Optoelectronic Devices · Georgia Tech
Tried and failed
in situ magnesium doping during epitaxial growth applied to hexagonal boron nitride thin films. Reason: extremely low electrical activation efficiency of incorporated magnesium dopant atoms
Advancing the Integration of 2d h-BN in Optoelectronic Applications · Georgia Tech
Tried and failed
nonmetal doping with phosphorus applied to semiconductor photocatalysts. Outcome: worse than baseline. Reason: deep midgap states acted as electron traps rather than facilitating catalytic charge transfer
Tried and failed
cryogenic cooling of semiconductor devices applied to wide-bandgap p-channel field-effect transistors. Outcome: worse than baseline. Reason: incomplete dopant ionization at low temperatures increased sheet and contact resistance, reducing drive current
GaN Complementary-Metal-Oxide-Semiconductor (CMOS) Technology · MIT
Considered and rejected
Considered and rejected: Silicon doping for n-type B-III-V alloys was rejected due to lack of dopant activation, requiring GaTe/Te evaporation instead.
III-V optoelectronic devices in the BGaInAs material system · UT Austin
Lattice distortion, carrier scattering, and mobility degradation from dopant incorporation
Introducing substitutional, interstitial, or surface adatom dopants frequently distorted host crystal lattices and induced mechanical stress. These structural perturbations increased carrier scattering, disrupted electronic band structures, and drastically degraded carrier mobility.
Lost to a baseline
Field-effect mobility of 1.5% Nb-doped p-type MoS2 (1.43 cm2V-1s-1) was lower than pristine n-type MoS2 due to lattice distortion from substitutional doping.
Towards Scalable Electronics: Synthetic 2D Materials for Large-Area 2D Circuit Integration · EPFL
Considered and rejected
Considered and rejected: P-doped and n-doped SOI device layers rejected in favor of undoped silicon due to doping-induced residual stress causing face sheet warping.
Stress-resilient electromagnetically actuated deformable mirror · OpenBU
Considered and rejected
Considered and rejected: Rejected transition metal oxides (MoO3, V2O5) surface-transfer doping due to drastic carrier mobility degradation at high carrier densities and integration difficulty
Diamond on GaN integration for power semiconductor devices with efficient thermal management · EPFL
Considered and rejected
Considered and rejected: Rejected conventional interstitial doping to control drain electric fields because it damages the pristine CNT lattice.
Considered and rejected
Considered and rejected: Rejected chemical doping as the disorder-tuning method because it shifts the chemical potential and alters lattice constants/electronic structures.
Study of superconductivity in quantum materials using controlled disorder · Iowa State
Considered and rejected
Considered and rejected: Rejected direct substitutional doping of CNT lattice because it disrupts sp2 bonding, increases scattering, and reduces carrier mobility.
Tried and failed
random substitutional doping applied to 1D nanostructure electronic transport. Outcome: no signal. Reason: random dopants failed to enhance conductance while adding parasitic mass without targeted electronic interaction
Computational design of carbon nanotube sensors for gas phase explosives detection · UT Austin
Tried and failed
adatom surface doping applied to 2D topological insulator stanene. Reason: Adatoms caused excessive electronic band structure disruption or unwanted metallization instead of controlled semiconducting doping
High-performance predictions of electron and phonon transport from first principles · Harvard
Excessive dopant concentration and overdoping leading to phase separation, clustering, or material degradation
Exceeding optimal doping concentrations led to dopant precipitation, secondary phase segregation, or dopant clustering that quenched photoluminescence. High dopant loadings also disrupted organic molecular packing, degraded active layer crystallinity, and caused physical rupturing of thin films.
Tried and failed
transition metal oxide high-concentration surface doping applied to semiconductor photoanodes for pollutant degradation. Outcome: worse than baseline. Reason: excessive loading lowered the valence band redox potential too much, reducing oxidation capacity
The Development of Energy Efficient Wastewater Treatment: Electrochemical Oxidation and PFACs liquid-liquid Extraction · Georgia Tech
Tried and failed
high-concentration chemical doping applied to conjugated polymer thermoelectric materials. Outcome: worse than baseline. Reason: severe structural disruption of lamellae caused over-doping, decreasing Seebeck coefficient without increasing electrical conductivity
Examining thermal and charge transport in organic materials with pi-electron interactions · Georgia Tech
Tried and failed
excessive chemical dedoping of hole transport layer applied to perovskite solar cells. Outcome: worse than baseline. Reason: degraded current density, fill factor, and reduced active layer crystallinity
Fabrication and characterization of lead-free and lead based perovskite solar cells · Imperial
Tried and failed
high-concentration substitutional cation doping applied to perovskite metal oxide nanoparticles. Reason: Dopant concentration exceeded solubility limits, forming secondary impurity phases rather than single-phase perovskite.
Tried and failed
transition metal dopant incorporation applied to semiconductor nanocrystals. Outcome: worse than baseline. Reason: dopant clustering caused parasitic emission and quenched excitonic photoluminescence quantum efficiency
Charge Carrier Localisation in Metal Halide Perovskites for Optoelectronic Applications · Cambridge
Considered and rejected
Considered and rejected: Rejected AuCl3 doping concentrations above 10 mM and non-polar solvents because they caused graphene sheets to rupture.
Chemical approaches for improved nanoscale organic and polymer thin-film transistors (TFTs) · UT Austin
Considered and rejected
Considered and rejected: Rejected heating low-melting solids/high-boiling liquids for vapor doping due to condensing/overdoping and atmospheric reactions.
INELASTIC ELECTRON TUNNELLING SPECTROSCOPY (lETS) OF SILANE COUPLING AGENTS · De Montfort Open Research Archive (DORA)
Tried and failed
increasing dopant precursor flow rate in vapor deposition applied to wide-bandgap semiconductor epitaxial thin films. Reason: excess dopant flow caused high-density parasitic surface particle formation and degraded structural quality
Hexagonal boron nitride for deep UV applications · Georgia Tech
Lattice damage and lateral straggle from ion implantation and bombardment
High-energy ion implantation and bombardment created severe crystal lattice damage that degraded critical temperatures and destroyed electronic transport. Furthermore, implant straggle and defective regions induced permanent device failure under bias or thermal cycling.
Tried and failed
low-energy ion implantation for carrier doping applied to two-dimensional superconductor flakes. Outcome: worse than baseline. Reason: implantation reduced critical temperature instead of enhancing it, likely due to lattice damage
Modulation of superconductivity in two-dimensional materials · UT Austin
Tried and failed
blanket ion implantation and plasma exposure applied to semiconductor lateral diodes. Outcome: unstable. Reason: caused severe electrical degradation and permanent device failure upon cryogenic thermal cycling
Formation, integration, and control of semiconductor spin-defects in electronic and photonic devices · Harvard
Tried and failed
blanket hydrogen ion implantation applied to semiconductor diode devices. Reason: caused severe electrical degradation and permanent device failure upon cryogenic cooling to 4 K
Solid-State Quantum Memories for Near-Term Quantum Repeaters · MIT
Tried and failed
selective ion implantation using shadow masking applied to vertical semiconductor power field-effect transistors. Outcome: worse than baseline. Reason: insufficient metal masking or lateral implant straggle damaged the drift region, severely degrading current density
Novel Structures for Scalable Vertical Gallium Nitride Power Devices · MIT
Considered and rejected
Considered and rejected: Rejected ion implantation for doping Si films due to lattice damage requiring high-temperature activation and the risk of unintentionally implanting into the underlying SiC.
Microstructural and electrical characterization of Si/4H-SiC heterojunction diodes · DSpace-CRIS at TU Wien
Considered and rejected
Considered and rejected: Rejected ion bombardment (2 MeV He+) as the defect-inducing mechanism because the induced external defects lack long-term thermodynamic stability compared to chemical doping.
Low Energy Order-To-Disorder Transition Pathways In Phase-Change Nanowires · ScholarlyCommons at Penn
Considered and rejected
Considered and rejected: Rejected vertical doping-based Super Junctions in GaN due to inefficient Mg p-type doping and lack of effective implantation/regrowth.
New Technologies to Enhance the Figures-of-Merit of GaN Power Devices · EPFL
Thermal instability, dopant diffusion, and profile redistribution
Doping profiles frequently redistributed or degraded when subjected to repeated thermal cycles, calcination, or high-temperature operation. In other instances, volatile dopant species thermally desorbed or diffused across interfaces, leading to component loss and electrical degradation.
Considered and rejected
Considered and rejected: Rejected standard MOSFET and BJT architectures for 3DI because multi-impurity doping profiles redistribute and degrade under repeated thermal cycles required for upper layers.
Considered and rejected
Considered and rejected: Rejected doping prior to top silicon layer thinning in favor of doping after thinning down to ~40 nm, which reduced the required dopant amount and improved RTA dopant profile uniformity across depth.
Nanofabrication, measurement, and microscopy of ~10 nm scale single electron transistors · Imperial
Tried and failed
B-site transition metal doping in perovskites applied to thermochemical water splitting redox cycling. Outcome: unstable. Reason: Doping caused surface cation segregation and volatile component loss during high-temperature cycling
Tried and failed
transition metal doping with high-temperature calcination applied to photocatalytic nitrogen reduction. Outcome: worse than baseline. Reason: high-temperature calcination of metal dopants lowered photocatalytic activity compared to undoped material
Influence of Carbon and Oxygen for Photocatalytic Nitrogen Fixation on Titania · Georgia Tech
Considered and rejected
Considered and rejected: Rejected p-GaN cap or delta-doping for PSJ charge matching due to Mg memory effect, thermal back-diffusion, and temperature-dependent carrier mismatch causing early breakdown.
New Technologies to Enhance the Figures-of-Merit of GaN Power Devices · EPFL
Tried and failed
transition metal chloride chemical doping applied to carbon nanotube films. Outcome: unstable. Reason: Dopant thermally decomposed and desorbed at moderate elevated temperatures, causing significant loss of electrical conductivity.
Continuous carbon nanotube films for thermoelectric applications · Imperial
Considered and rejected
Considered and rejected: Rejected post-doping graphene transfer because water/solvents and 180 °C adhesion annealing remove surface corona charge and HMDS layers; adopted pre-transfer ion drive-in instead.
Graphene transparent conductors for tandem photovoltaic cells · Oxford
Unintentional doping and mobility degradation from chemical processing and ambient exposure
Uncontrolled environmental exposure, chemical wet stripping, and etching solutions caused unintended doping and carrier contamination. These processing steps degraded carrier mobility, inverted doping polarity, and created parasitic charge extraction barriers.
Considered and rejected
Considered and rejected: Rejected MoO3 and polymeric interlayers because MoO3 causes p-type doping/off-state degradation and polymer solvents damage the PFBT SAM.
Analysis of the Contact Resistance of Organic Thin-Film Transistors · EPFL
Tried and failed
slow cooling during post-annealing thermal processing applied to inorganic perovskite solar cells. Outcome: worse than baseline. Reason: oxygen-induced surface p-doping created a charge extraction barrier at the electron transport interface
Formation pathways and phase behaviour of CsPbI2Br: toward stable and reproducible solar sells · Imperial
Considered and rejected
Considered and rejected: Ferric chloride and ferric nitrate Cu etchants rejected due to heavy unintentional p-doping of graphene.
The modification of graphene band structure by periodic potential perturbation · Cambridge
Tried and failed
wet chemical gate dielectric stripping applied to epitaxial graphene electronic devices. Reason: acid etchant caused severe chemical contamination, reversed carrier doping, degraded mobility, and destroyed edge transport states
The Edge States of Epitaxial Graphene on SiC · Georgia Tech
Tried and failed
prolonged ambient oxidative doping before metallization applied to quantum dot hole transport layers. Outcome: worse than baseline. Reason: excessive ambient exposure increased series resistance and reduced initial power conversion efficiency
Considered and rejected
Considered and rejected: Thermal annealing on graphene/SiO2 was avoided because it increases doping and decreases mobility via strong substrate interactions.
High Quality Graphene For Sensing And Automotive Applications · IRIS - SNS - prod
Left open by the authors
Problems the authors named and did not get to.
Left open
Investigate fundamental mechanisms to improve etch selectivity between silicon nitride and silicon dioxide in plasma-enhanced atomic layer etching simulations. Blocker: Vague direction without specified parameter sets, chemical surface chemistries, or target selectivity thresholds
Left open
Use ion implantation to achieve full lithiation (x ~ 1) of LixNbO2 prior to device encapsulation. Blocker: Requires a physical semiconductor fabrication facility and ion implantation equipment
Adaptive Oxide Based Low-Power Memristive Devices for Neuromorphic Computing · Georgia Tech
Left open
Perform ion implantation experiments using Ar species instead of N on PIN rectifiers to reduce reverse leakage current. Blocker: Requires a semiconductor fabrication facility, ion implanter, and characterization equipment.
Development, Fabrication and Characterization of III-Nitride Bipolar Devices: Rectifiers, Avalanche Photodiodes, and Laser Diodes · Georgia Tech
Left open
Engineer SiGe HBT device doping profiles to reduce temperature-dependent variability enhancement at cryogenic temperatures. Blocker: Requires semiconductor device fabrication facilities or proprietary TCAD process simulation tools
Using SiGe HBTs for quantum science at deep cryogenic temperatures · Georgia Tech
Left open
Experimentally implement selective boron emitter (p++/p+) structures on single-side n-TOPCon silicon solar cells. Blocker: Requires cleanroom wet chemistry, ion implantation, ALD/PECVD/LPCVD equipment, and silicon fabrication facilities.
Development of low-cost high-efficiency tunnel oxide passivated contact silicon solar cells · Georgia Tech
Left open
Experimentally characterize the trade-off between mean dose throughput and dose uniformity in ion implantation optimization. Blocker: Requires access to physical semiconductor manufacturing equipment (ion implanter) and fab facilities
Applications of Probabilistic Machine Learning Models to Semiconductor Fabrication · MIT
Left open
Investigate diode response under H implant, DI water boil, and 400 °C RTA for simultaneous T-center synthesis and contact annealing. Blocker: Requires a semiconductor fabrication and characterization wet lab (H ion implantation, rapid thermal annealing, electrical testing).
Solid-State Quantum Memories for Near-Term Quantum Repeaters · MIT
Left open
Demonstrate inverse hybrid bonding on a wafer-to-wafer testbed with etched silicon through-holes for precursor vapor transport. Blocker: Requires a semiconductor cleanroom/fabrication lab, silicon etching, and ALD/vapor-phase bonding apparatus.
Dense Interconnect and Power Delivery Technologies for 3-D Heterogeneous Integration Architectures · Georgia Tech
Left open
Develop reliable SCALES selective KOH etching on n-type phosphorus-doped Si substrates and explore pre-formed silicide contacts. Blocker: Requires a semiconductor nanofabrication cleanroom, chemical wet lab, and physical Si substrate processing.
Engineering a self-aligned metal-oxide-semiconductor gate stack for nano-modular device fabrication · Georgia Tech
Left open
Fabricate AlGaN avalanche photodiode devices on AlN substrates using nitrogen ion implantation for electrical isolation. Blocker: Requires semiconductor cleanroom fabrication equipment, MOCVD growth, and an ion implanter.
HIGH PERFORMANCE III-NITRIDE ULTRAVIOLET AVALANCHE PHOTODETECTORS · Georgia Tech
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