Zn incorporation and band gap shrinkage in p-type GaAs

Abstract

Dimethylzinc (DMZn) was used as a p-type dopant in GaAs grown by low pressure metalorganic vapor phase epitaxy using trimethylgallium and arsine (AsH3) as source materials. The hole carrier concentrations and zinc (Zn) incorporation efficiency are studied by using the Hall effect, electrochemical capacitance voltage profiler and photoluminescence (PL) spectroscopy. The influence of growth parameters such as DMZn mole fraction, growth temperature, and AsH3 mole fraction on the Zn incorporation have been studied. The hole concentration increases with increasing DMZn and AsH3 mole fraction and decreases with increasing growth temperature. This can be explained by vacancy control model. The PL experiments were carried out as a function of hole concentration (1017–1.5×1020 cm−3). The main peak shifted to lower energy and the full width at half maximum (FWHM) increases with increasing hole concentrations. We have obtained an empirical relation for FWHM of PL, ΔE(p)(eV)=1.15×10−8p1/3. We also obtained an empirical relation for the band gap shrinkage, ΔEg in Zn doped GaAs as a function of hole concentration. The value of ΔEg(eV)=−2.75×10−8p1/3, indicates a significant band gap shrinkage at high doping levels. These relations are considered to provide a useful tool to determine the hole concentration in Zn doped GaAs by low temperature PL measurement. The hole concentration increases with increasing AsH3 mole fraction and the main peak is shifted to a lower energy side. This can be explained also by the vacancy control model. As the hole concentration is increased above 3.8×1018 cm−3, a shoulder peak separated from the main peak was observed in the PL spectra and disappears at higher concentrations.

Optical and Transport Properties of p-Type GaAs

“…For pure GaAs the value of band gap is usually found to be near 1.4 eV (Omar 2003, BoylStad 2002, here present authors obtained the value a little lower than that which may be the ). Usually band gap narrowing occurs in GaAs at higher impurity levels (Hudait et al 1997, El-Nahass 2011 and it is directly proportional to the cubic root of carrier concentration.…”

“…The hole carrier concentrations of Zn doped GaAs was studied by using the Hall effect (Hudait et al 1997). The hole concentration and mobility in wafers from (001) monocrystal GaAs doped with Zn was measured by the Hall effect method (Mihailova 2005) under constant electrical and magnetic fields.…”

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

“…The FWHM, DE(n) of the B-B peak at 4.2 K of PL spectra increases with increasing electron concentration. The broadening of FWHM in Si-doped GaAs is similar to that in C-doped GaAs [53], Be doped GaAs [5] and Zn-doped GaAs [11,54] and can be explained by band to band optical transitions with and without momentum (k) conservation between the conduction and valence bands [11]. Alternatively, this can be explained in terms of the impurity band merging with the valence band edge and it becomes band tail states at high doping concentrations.…”

“…Good experimental agreement has been obtained for Eq. (10) in the cases of p-GaSb and p-GaAs [54,60]. Earlier work [61] on the group IV semiconductors Si and Ge using essentially the same formulation as Eq.…”

Low temperature photoluminescence properties of Zn-doped GaAs

“…An increase in P AsH 3 /P TMGa will increase in gallium vacancy concentration, hence, the incorporation of Zn on Ga site increased. The hole concentration thus increased when the AsH 3 mole fraction is increased [32]. According to analysis of Vechten [33,34] the vacancy migration reaction occurring in GaAs growth can be expressed as:…”