Sb Diffusion Research Articles

Gasb-to-Si Direct Wafer Bonding and Thermal Budget Considerations for Photonic Applications

Extensive progress has been made in recent years in heterogeneous integration (HI) of III-V materials on Si photonics wafers [1], including direct chip-to-chip bonding of GaSb-based infrared (IR) lasers [2], greatly expanding the application space and performance of either material system on its own. This includes active research at Sandia National Labs developing lasers based on GaAs, GaSb, GaN, and InP substrates directly integrated with silicon photonics at the chip and wafer scale. A “device last” process flow is desirable in this case both for scalability and because of the tight alignment tolerance required between the Si waveguides and active III-V laser elements to optimally couple light between the III-V and the Si. In this process flow, the Si photonics wafer is fabricated separately before bonding with an unpatterned III-V wafer or chip. The III-V laser is then defined after bonding, allowing lithographic registration to Si photonics structures. Thus, preparation of both semiconductor surfaces and preservation of the bond between them become critical for device performance and constrain subsequent process steps. Here, we focus on GaSb-based devices.The first consideration is preparing the GaSb and Si surfaces for bonding. Argon sputtering to prepare the GaSb surface for bonding to Si has been investigated, though the emphasis was on GaSb surface roughness, bonding temperature, and electronic transport through the interface [3]. Here, we use x-ray photoelectron spectroscopy (XPS) to investigate the impact of the GaSb oxide composition on the quality of the bond to oxidized Si wafers. In Fig. 1(a)-(c) we use confocal scanning acoustic microscopy (CSAM) to compare as-received 3” GaSb substrates with and without chemical oxide removal to epitaxial GaSb. In the CSAM images, dark areas indicate bond adhesion. We find that bonding improves with decreasing Ga-oxide content realized on the epitaxial GaSb.The second consideration is constraining the laser process steps in order to preserve the bond between the Si photonics and GaSb wafers. Our HI process steps involving GaSb thinning and substrate removal have been described elsewhere [4], though investigation of the thermal budget for survival of the direct GaSb/Si bond through a laser fabrication process flow is lacking in the literature. As the thermal expansion coefficient of GaSb is approximately three times that of Si, temperatures must be limited to prevent the GaSb from expanding excessively and delaminating from the Si wafer when running the III-V laser fabrication after integration with the Si photonics wafer. We investigate the robustness of the bond between epitaxial GaSb and the Si photonics wafer through cross-sectional transmission electron microscopy (TEM) of the bond interface after various process steps typical to laser fabrication and the implications of the thermal budget on these process steps. For example, we find that extended periods of time (more than an hour) at 250°C, which is typical for chemical vapor deposition (CVD) of SiO2 or Si3N4, cause the thinned III-V wafer to delaminate from the Si photonics wafer. While we don’t observe destructive delamination at lower processing temperatures, high-angle annular dark-field imaging (HAADF) analysis in Fig. 1(d) shows significant Sb diffusion into the Si photonics native SiO2 layer.In summary, for optimal performance of GaSb-based hybrid lasers directly bonded to Si photonics, understanding and preserving the bond between these materials is critical. These considerations include minimizing the Ga-oxide at the GaSb surface prior to bonding to promote bond success and keeping extended thermal processes below 250°C to maintain the bond between the GaSb and the Si photonics wafers. These results will inform processes required for full laser fabrication flow, particularly in steps that traditionally require higher or longer temperature parameters.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.[1] D. Caimi, et al., IEEE Trans. Elect. Dev. 68, p. 3149 (2021).[2] A. Spott, et al., Optica 5, p. 996 (2018).[3] F. Predan, et al., Appl. Surf. Scie., 353, p. 1203 (2015).[4] M. Wood, et al., in CLEO 2023 Technical Digest Series, STh3H.5 (2023). Figure 1

On determining the surface segregation kinetics of Sb in binary and ternary Fe alloys during continuous annealing

In the present research, Sb surface segregation kinetics for Fe-(0.01/0.03)Sb and Fe-2Mn-(0.01/0.03)Sb at.% alloys were determined based on the modified Darken model and linear heating followed by isothermal annealing. The modified Darken model was used to evaluate the measured Sb segregation profile during continuous galvanizing heat treatments. Based on the kinetic analysis, increasing temperatures and isothermal holding times led to an increase in Sb surface segregation. Sb segregation was observed at the surface for both the Fe-xSb and Fe-2Mn-xSb alloys after annealing. It was found that Sb surface diffusion in the Fe-Sb alloys was faster than in the Fe-2Mn-Sb alloys, which was attributed to the crystal structure and the defect density in the matrix. The segregation rate was determined from the Darken curves and a higher segregation rate was observed in Fe-xSb alloys. The activation energy of Sb diffusion for the Fe-Sb and Fe-2Mn-xSb alloys was determined to be ∼ 193±18 kJ/mol, which is close to the activation energy of bulk Sb diffusion in α-Fe.

A comparison of Ge, Sb and Te thermal diffusion through Ge2Sb2Te5

Chalcogenide Ge-Sb-Te alloys are used in a new generation of nonvolatile memories named Phase Change Memories which can be thermally switched from low resistivity to high resistivity states by feeding the memory cells with appropriate electrical pulses. During their lifetime, the heterogeneous redistribution of the elements within the active region of the cells is at the origin of the drift of their electrical characteristics and, ultimately, of their failure. Up to now, little is known about the relative diffusivities of the atomic elements that compose the alloys, what hampers the modeling and optimization of the materials and devices. Here, we report an experimental study of the thermal diffusion of Ge, Sb and Te through Ge2Sb2Te5. For this purpose, specific structures consisting of a layer of Ge, Sb or Te sandwiched between two Ge2Sb2Te5 layers have been fabricated and annealed at various temperatures and times. Using transmission electron microscopy based techniques, we evidence that Te diffusion can be activated from about 160 °C while Ge and Sb needs much higher temperatures, 220 °C and 350 °C, respectively. These results are in disagreement with previous theoretical simulations predicting that Ge is the most diffusive element while Te is the least.

Highly efficient spin current source using BiSb topological insulator/NiO bilayers

BiSb is a topological insulator with both giant spin Hall effect and high electrical conductivity, which are important for ultralow power spin–orbit-torque magnetoresistive random access memory. However, when a ferromagnetic (FM) thin film is deposited on top of BiSb, large surface roughness and diffusion of Sb out of the BiSb layer into the FM layer results in a much smaller effective spin Hall angle In this work, we show that by inserting a NiO layer between BiSb and Co, we can significantly improve of BiSb and induce perpendicular magnetic anisotropy at the NiO/Co interface. We obtained a large = 10.3 for the BiSb bottom layer at the NiO layer thickness of 3 nm, which is comparable to the best of BiSb top layer studied so far. Our study shows that BiSb/NiO bilayers are promising for integration of BiSb to SOT-MRAM.

Probing High-Temperature Oxidation of Thermoelectric Phases Yb14MSb11 (M = Mg, Mn, Zn).

Yb14MSb11 (M = Mg, Mn, Zn) are p-type Zintl phases with high thermoelectric efficiencies at 1000 °C and melting points above 1200 °C under vacuum and/or inert atmosphere. In a thermoelectric generator, even within a vacuum jacket, small amounts of oxygen may be present, and therefore, elucidating chemical reactions in the presence of air or oxygen provides a framework for engineering design. The oxidation of Yb14MSb11 was investigated from room temperature to 1000 °C in dry air with thermogravimetric/differential scanning calorimetry (TG/DSC) on small pellets and visually after heat treatment to 1000 °C under ambient conditions on large pellets. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and powder X-ray diffraction provide identification of the oxidation products. In the presence of dry air, Yb14MSb11 initially oxidizes initially slowly at room temperature with a sweeping exotherm and weight gain with rapid oxidation at 400 °C, after which the exotherm signal plateaus at about 600 °C, with M = Zn showing the smallest overall exothermic curve. All samples showed a paired endo-/exotherm at 785-803 °C, consistent with the melting/solidification of YbSb2, which in the case of M = Mg, Mn extrudes from the sample. The various sections of the pellets─outer layer, inner layer, and core are analyzed, and oxidation reactions are proposed. After cycling to 1000 °C, the outer layer is composed of Yb2O3 with small amounts of the corresponding metal oxides. The inner layer shows delamination by inward diffusion of oxygen and outward diffusion of Sb or Sb oxide-containing phases, and the core shows Yb14MSb11. Yb14ZnSb11 shows the best resistance to oxidation and may provide a promising material for further passivation optimization.

Ex-situ n-type heavy doping of Ge1-xSnx epilayers by surface Sb deposition and pulsed laser melting

Ge1-xSnx alloys have attracted considerable attention for their promising electrical and optical properties. One of the main challenges for their successful implementation in devices concerns the fabrication of n-type heavily doped surface layers. In this work, a new methodology for ex-situ doping of Ge1-xSnx layers is investigated. It consists of the deposition of Sb atoms on the surface of Ge1-xSnx layers followed by pulsed laser melting (PLM) that ensures the diffusion of Sb into the alloy. We demonstrate that Sb is incorporated very efficiently within a relaxed Ge0.91Sn0.09 epilayer, with supersaturated 4 × 1020 cm−3 active concentrations, in line with literature records obtained in Ge1-xSnx with in-situ approaches. At the same time, we observe that the concentration of substitutional Sn close to the surface decreases from 9 to about 6 at. % after PLM, inducing a contraction of the lattice parameter perpendicular to the underlying Ge1-xSnx. These results demonstrate a possible route for ex-situ n-type heavy doping of Ge1-xSnx alloys, but indicate also that Sn redistribution and precipitation phenomena need to be carefully considered for a successful process development.

Facile co-removal of As(V) and Sb(V) from aqueous solution using Fe-Cu binary oxides: Structural modification and self-driven force field of copper oxides

Currently, the environmental and ecological damage caused by As(V) and Sb(V) co-contamination has attracted widespread attention worldwide. Due to the similar intrinsic structure configuration and electrostatic repulsion of As(V) and Sb(V), the long-standing issue of their low co-removal capacity remains unresolved. In this study, novel Fe-Cu (FC) binary materials with varied Fe/Cu proportions were synthesized via a simple co-precipitation method to co-eliminate aquatic As(V) and Sb(V). A 2/1 ratio of Fe/Cu was determined to be a suitable proportion with a higher co-adsorption capacity, specifically 70.9 mg·g−1 for As(V) and 94.3 mg·g−1 for Sb(V). Detailed morphological and structural analyses indicated that the FC material gradually changed from microscale aggregates to nanoscale spheres with increasing Cu content, accompanied by an increasing crystalline degree and higher surface area. Additionally, the transformation of amorphous ferrihydrite (FO) into FeO(OH) was suppressed by Fe-Cu complexion during the co-adsorption process, in which ferrihydrite (FO) had more adsorption sites than FeO(OH). In addition, the addition of Cu promoted the pHpzc of FC materials from the acidic range into the neutral or alkaline range. The increased potential difference of FC materials accelerated the As(V) and Sb(V) diffusion rate and effectively offset native electrostatic repulsion, which exhibited a considerable effect than the adsorption sites. Through detailed kinetic data analysis, it was determined that the proportion of the diffusion layer thickness around Sb(V) was suppressed to the As(V) level, and the adsorption kinetics of the two species were both promoted by the self-driven force field. All the results indicated that the co-adsorption capacity depended on the coupling contribution of Fe and Cu, where Fe oxide acted as the major adsorption potential and Cu provided a self-driven force for As(V) and Sb(V) diffusion. This study may provide a novel prospective for homogeneous metal ion co-removal.

Melt-spun Sn1−−Sb Mn Te with unique multiscale microstructures approaching exceptional average thermoelectric zT

SnTe has attracted worldwide attention as a non-toxic candidate material for thermoelectric applications; however, un-modified SnTe possesses inferior thermoelectric properties. Herein, we report the significantly improved thermoelectric performance in Sb, Mn-codoped SnTe synthesized by energy-efficient melt spinning. Sb segregation was observed at the grain boundaries of Sb-doped and Sb, Mn-codoped SnTe melt-spun ribbons, leading to grain refinement; subsequent sintering promotes the diffusion of Sb while retains Sb-rich particles. Initially, intensified phonon scattering from unique multiscale microstructures, including point defects, Sb-rich particles and high-density dislocations generated after Sb doping, effectively diminishes the lattice thermal conductivity of SnTe, leading to a substantially low value of 0.55 W m −1 K −1 in Sn 0.84 Sb 0.16 Te at 300 K. Further, the power factors are significantly enhanced via Mn doping owing to valence band convergence, verified by first-principles calculation. Consequently, a peak zT of ~ 1.27 at 773 K and an exceptional average zT of ~ 0.89 over 300–873 K are obtained in Sn 0.72 Sb 0.16 Mn 0.12 Te, which are ~ 110% and ~ 340% higher than those of SnTe, respectively. This study provides an effective pathway to synergistically improve the thermoelectric performance of SnTe by microstructure and band structure engineering, and establishes melt spinning as a controllable synthetic method to high-performance thermoelectrics. Sb and Mn co-doped SnTe materials, synthesized by combining fast melt spinning and hot pressing, achieve synergistically diminished lattice thermal conductivity and improved power factor, due to enhanced phonon scattering from unique multiscale microstructures and band convergence, respectively. Notably, the Sn 0.72 Sb 0.16 Mn 0.12 Te sample delivers an excellent average zT of ~ 0.89 in the temperature range of 300–873 K. • Synthesizing Sb and Mn codoped SnTe by energy-efficient melt spinning. • Clarifying the vital role of Sb doping in grain refinement of melt-spun SnTe. • Diminishing the lattice thermal conductivity by multiscale microstructures. • Optimizing thermoelectric properties by structure and band engineering. • Obtaining an exceptional average zT of 0.89 (300–873 K) in Sn 0.72 Sb 0.16 Mn 0.12 Te.

Self-induced antimony compositional variation GaAs/Ga(As)Sb core-shell nanowires by molecular beam epitaxy

Self-catalyzed GaAs/GaAsSb heterojunction nanowires (NWs) were grown on Si (111) substrate by molecular-beam epitaxy (MBE). The GaAs/GaAsSb heterojunction NWs were determined by XRD and Raman spectra. Antimony (Sb) compositional variation of GaAs/Ga(As)Sb heterojunction NWs have been clearly evidenced by XRD spectrum, energy-dispersive X-ray (EDX) spectroscopy combined with absorption spectra. Detailed electron microscopy investigations indicate that the As-Sb exchange at the GaAsSb NWs surface during growth resulting in an outward diffusion of Sb (and corresponding inward diffusion of As), the structure of GaAs/GaAsSb/GaSb and GaAsSb/GaSb core-shell NWs were formed. This study offers a possibility to grow ternary III-V NWs with complex structures that can be used for electronic and optoelectronic applications.

Interfacial behaviors of p-type CeyFexCo4–xSb12/Nb thermoelectric joints

Interfacial diffusions and/or chemical reactions are one of the key issues for the reliability of CoSb3-based skutterudite thermoelectric (TE) joint, especially for the [Formula: see text]-type joint, which limits the applications of TE devices. We investigate the interfacial evolution for [Formula: see text]-type CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints ([Formula: see text]–1, [Formula: see text], 3, 4) and combine the previous study on [Formula: see text]-type Yb[Formula: see text]Co4Sb[Formula: see text]/Nb joint to demonstrate the effect of TE materials on the interfacial microstructure and interfacial resistivity. The reaction–diffusion kinetic analysis shows that the TE materials has little effect on chemical reactions but strongly influence the Sb diffusions. The low energy barrier of Sb diffusion leads to the absent phase decomposition of skutterudites in CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints. The interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints is related with Fe content and the interfacial reaction layer (IRL) growth. In addition, since the interfacial reaction layer growth rate and interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints are both low, Nb is an adequate barrier layer candidate material.

Interdiffusion Studies in the Co-Sb System

CoSb based compounds have gained much importance in the fields of thermoelectric devices. In this work, we have conducted the solid–state conventional bulk diffusion couple experiments. To study the phase evolutions, Co/Sb diffusion couples are annealed at 450–550 °C. The interdiffusion zone is analysed using field emission gun equipped scanning electron microscope and the composition measurements are done in electron probe micro−analyser to confirm the growth of various product phases. The marker experiment indicates that the CoSb3 phase grows mainly by diffusion of Sb in the binary Co–Sb system. Growth of the CoSb3 phase is discussed based on assessment correlating the difference in mobilities of species with the high homologous temperature, crystal structure of the phase, and the concept of sublattice diffusion mechanism in line compounds.

Atomic-resolution interfacial structures and diffusion kinetics in Gd/Bi0.5Sb1.5Te3 magnetocaloric/thermoelectric composites

The demand of a full solid-state cooling technology based on magnetocaloric and thermoelectric effects has led to a growing interest in screening candidate materials with high-efficiency cooling performance, which also stimulates the exploration of magnetocaloric/thermoelectric hybrid cooling materials. A series of Gd/Bi0.5Sb1.5Te3 composites was fabricated in order to develop the hybrid cooling technology. The chemical composition, phase structure and diffusion kinetics across the reaction layers in Gd/Bi0.5Sb1.5Te3 composites were analyzed at different reaction temperatures. Micro-area elemental analysis indicates that the formation of interfacial phases is dominated by the diffusion of Gd and Te while the diffusion of Bi and Sb is impeded. The interfacial phases, including GdTe2, GdTe3, and intermediate phases GdTex, are identified by atomic-resolution electron microscopy. The concentration modulation of Gd and Te is adapted by altering the stacking of the Te square-net sheets and the corrugated GdTe sheets. Boltzmann-Matano analysis was applied to reveal the diffusion kinetics of Gd and Te in the interfacial layers. The diffusion coefficients of Te in GdTe2 and GdTe3 are much higher than that of Gd while in GdTe the situation is reversed. This study provides a clear picture to understand the interfacial phase structures down to an atomic scale as well as the interfacial diffusion kinetics in Gd/Bi0.5Sb1.5Te3 hybrid cooling materials.

Investigation on thermal stability of vanadium-doped Sb2Te phase change material

Transition metal elements doping can greatly improve the usability of Sb–Te for phase change memory. In this paper, we focused on the thermal stability of transition vanadium (V)-doped Sb2Te (VSb2Te) films with different V concentration which were prepared by co-sputtering. The effects of V doping on the crystallization and microstructure properties of Sb2Te were studied by temperature-dependent resistance measurements, in-situ heating TEM and HRTEM observation, respectively. With increasing V content, the crystallization is inhibited and the data retention is obviously enhanced, and the grain size shrinks significantly. Ab initio molecular dynamics simulation was used to explain the mechanism of the improved thermal stability and the results show that the diffusion of Sb and Te atoms are suppressed by doped V, which may account for the high thermal stability of VSb2Te.

Study of TaN and TaN-Ta-TaN thin films as diffusion barriers in CeFe4Sb12 skutterudite

The efficiency of thermoelectric devices depends on phase stability of layers constituting the device. TaN and TaN-Ta-TaN thin films, 900 nm thick, were investigated as diffusion barriers for the CeFe4Sb12 thermoelectric substrate in contact with the Cu electrode. It is shown that Sb diffuses through the TaN layer when the sample is heated above 400 °C. Multilayer TaN-Ta-TaN acts as the diffusion barrier for Sb and is efficient up to 500 °C. When diffusion of Sb occurs above 400 °C for TaN and above 500 °C for TaN-Ta-TaN, the formation of FeSb2 and Cu2Sb precipitates was identified by XRD and TEM/energy dispersive X-ray spectroscopy.

Self-limiting Sb monolayer as a diffusion source for Ge doping

A new method for the creation of high-quality, fully electrically active junctions to be applied in nanostructured semiconductor materials is explored in this work. The method consists in a gas phase antimony deposition on Ge, which gives rise to an antimony self-limiting behavior to form a monolayer (ML) on the Ge (100) surface. The ML formation is characterized by a wide thermal process window in terms of time and temperature. Synchrotron radiation Angle Resolved X-ray Photoelectron Spectroscopy shows that the ML structure consists in oxidized Sb grown over a very thin layer of Ge oxide, and a small amount of metallic Sb is embedded beneath the Ge surface during the deposition process. Interestingly, during the ML formation process native Ge oxide is reduced without the need of strong acid pre-treatments. By performing further thermal annealing in equilibrium conditions, Sb diffusion can be faithfully described by a well assessed diffusion model. Finally, processing the Sb monolayer with Pulsed Laser Melting technique, which is a strongly out-equilibrium diffusion process, allows to exploit the entire Sb ML as a dopant source, thus achieving junctions with a very high dopant concentration (1.2 × 1020 cm−3 Sb surface concentration) and a 100% Sb electrical activation.

Influence of Annealing on the Properties of Ge:Sb/Si(001) Layers with an Antimony Concentration Above Its Equilibrium Solubility in Germanium

The influence of rapid thermal annealing on the electrical and radiative properties of Ge:Sb/Si(001) epitaxial layers with an antimony concentration substantially higher than its equilibrium solubility in germanium is investigated. Local variations in the electrical and luminescence properties of n-Ge/Si(001) throughout the structure depth are investigated by means of the precise chemical etching of Ge. It is shown that a variation in the properties of such layers at relatively low (≤500°C) annealing temperatures (decrease in the electron concentration and photoluminescence intensity) occur in the absence of the noticeable diffusion-related redistribution of dopant atoms. Variations in the electrical and luminescence properties of Ge:Sb layers at relatively high (≥700°C) annealing temperatures are caused by the substantial redistribution of Sb due to its bulk diffusion and desorption from the surface. In particular, Sb diffusion leads to the formation of doped layers in initially undoped parts of the studied structures, which start to give a substantial contribution to the resulting conductivity of the structure and its photoluminescence signal.

Atomic resolution of interface diffusing in short-period InAs/GaSb superlattice

High-angle annular dark-field (HAADF) and electron energy loss spectroscopy in a Cs-corrected scanning transmission electron microscope were utilized for characterizing the interfacial chemical structure of the short-period InAs/GaSb superlattices with atomic resolution. The interfacial features determined from HAADF image contrasts and elemental composition profiles demonstrated that each interface width remains below 4.8 monolayers for all elements, while InAs-on-GaSb interfaces are sharper than GaSb-on-InAs interfaces. Tensile mapping revealed that the In and Sb diffusion at the interface may influence more than the other two elements and modulate the realistic lattice in the sublayers.

Oxygen filling voids and direct element imaging of metastable ZnSb structures by aberration-corrected scanning transmission electron microscopy

Void formation in metastable ZnSb structures has yet to be investigated. We developed a technique to fill voids caused by Sb diffusion, through the introduction of oxygen dopants into the metastable ZnSb phase. This filling of voids enables their role in phase-change processes to be accurately investigated. Our scanning transmission electron microscopy investigations showed that oxygen dopants repaired voids through recovery of bond connectivity. This approach stabilizes a metastable phase and avoids the metastable-to-stable phase transformation. Our characterization of void defects sheds light on the long-standing puzzle of the metastable-to-stable phase transition mechanism.

Pulsed laser diffusion of thin hole-barrier contacts in high purity germanium for gamma radiation detectors

A new method for the formation of hole-barrier contacts in high purity germanium (HPGe) is described, which consists in the sputter deposition of a Sb film on HPGe, followed by Sb diffusion produced through laser annealing of the Ge surface in the melting regime. This process gives rise to a very thin ( $ \le 100$ nm) n-doped layer, as determined by SIMS measurement, while preserving the defect-free morphology of HPGe surface. A small prototype of gamma ray detector with a Sb laser-diffused contact was produced and characterized, showing low leakage currents and good spectroscopy data with different gamma ray sources.

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate that As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex situ Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 1016 cm−3 hole density in polycrystalline CdTe films by As and P diffusion.