Si incorporation and Burstein-Moss shift in n-type GaAs

Abstract

Silane (SiH₄) was used as an n-type dopant in GaAs grown by low pressure metalorganic vapor phase epitaxy using trimethylgallium (TMGa) and arsine (AsH₃) as source materials. The electron carrier concentrations and silicon (Si) incorporation efficiency are studied by using Hall effect, electrochemical capacitance voltage profiler and low temperature photoluminescence (LTPL) spectroscopy. The influence of growth parameters, such as SiH₄ mole fraction, growth temperature, TMGa and AsH₃ mole fractions on the Si incorporation efficiency have been studied. The electron concentration increases with increasing SiH₄ mole fraction, growth temperature, and decreases with increasing TMGa and AsH₃ mole fractions. The decrease in electron concentration with increasing TMGa can be explained by vacancy control model. The PL experiments were carried out as a function of electron concentration (10¹⁷-1.5× 10¹⁸ cm^-3). The PL main peak shifts to higher energy and the full width at half maximum (FWHM) increases with increasing electron concentrations. We have obtained an empirical relation for FWHM of PL, ΔE(n) (eV)=1.4× 10^-8 n^1/3. We also obtained an empirical relation for the band gap shrinkage, δEg in Si-doped GaAs as a function of electron concentration. The value of ΔE_g (eV)=-2.75× 10^-8 n^1/3, indicates a significant band gap shrinkage at high doping levels. These relations are considered to provide a useful tool to determine the electron concentration in Si-doped GaAs by low temperature PL measurement. The electron concentration decreases with increasing TMGa and AsH₃ mole fractions and the main peak shifts to the lower energy side. The peak shifts towards the lower energy side with increasing TMGa variation can also be explained by vacancy control model.