Suppression of compensating native defect formation during semiconductor processing via excess carriers.

K Alberi,M A Scarpulla

doi:10.1038/srep27954

Abstract

In many semiconductors, compensating defects set doping limits, decrease carrier mobility, and reduce minority carrier lifetime thus limiting their utility in devices. Native defects are often responsible. Suppressing the concentrations of compensating defects during processing close to thermal equilibrium is difficult because formation enthalpies are lowered as the Fermi level moves towards the majority band edge. Excess carriers, introduced for example by photogeneration, modify the formation enthalpy of semiconductor defects and thus can be harnessed during crystal growth or annealing to suppress defect populations. Herein we develop a rigorous and general model for defect formation in the presence of steady-state excess carrier concentrations by combining the standard quasi-chemical formalism with a detailed-balance description that is applicable for any defect state in the bandgap. Considering the quasi-Fermi levels as chemical potentials, we demonstrate that increasing the minority carrier concentration increases the formation enthalpy for typical compensating centers, thus suppressing their formation. This effect is illustrated for the specific example of GaSb. While our treatment is generalized for excess carrier injection or generation in semiconductors by any means, we provide a set of guidelines for applying the concept in photoassisted physical vapor deposition.

Highlights

Underpinning the improvements were not well developed
The chemical potential that characterizes the reservoir is the Fermi level when the bands of the semiconductor are in thermal equilibrium
Realization of local equilibrium conditions depends on several factors, including the processing temperature, diffusion coefficients for atoms at the crystal surface and in the bulk, and chemical potentials

Summary

Introduction

Underpinning the improvements were not well developed. Understanding the relationships and interactions between defects, photogenerated carriers and the Fermi level is critical for assessing the potential for defect suppression via light stimulated processing techniques and can direct their implementation. In order to illustrate its utility, we apply this model to the concrete example of compensating native acceptor suppression during light-assisted epitaxy or annealing of nominally un-doped and intentionally n-type doped GaSb. In order to illustrate its utility, we apply this model to the concrete example of compensating native acceptor suppression during light-assisted epitaxy or annealing of nominally un-doped and intentionally n-type doped GaSb This material system exhibits dominant native defects of either positive or negative charge depending on the prevailing chemical potentials during processing and is ideal for assessing the influence of each. From these results, we have constructed a set of guidelines that can be applied to the light-assisted processing of semiconductors. Our findings have implications for physical vapor deposition techniques such as evaporation, hydride vapor phase epitaxy (HVPE) and molecular beam epitaxy (MBE) and especially for understanding differences between furnace and lamp-heated annealing treatments such as rapid thermal processing (RTP)

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Results

Conclusion