Ultrahigh-Purity Undoped GaAs Epitaxial Layers Prepared by Liquid Phase Epitaxy

Abstract

Ultrahigh-purity (UHP) GaAs epilayers have been grown reproducibly by liquid phase epitaxy (LPE) with conventional solution baking in a H2 environment. We have succeeded in achieving a high-purity (HP) n-type GaAs epilayer with a low electron carrier concentration of 5.84×1012 cm-3 and a high mobility of 312,000 cm2 V-1 s-1 at 77 K, which is the highest value ever reported. Photoluminescence (PL) analyses at 15 K for both UHP n-type and p-type GaAs epilayers were also performed. We have clarified that the PL intensity of an HP GaAs epilayer has a strong correlation with the mobility measured by Hall measurements at 77 K. The electron carrier concentration of the UHP GaAs epilayer also agrees very well with that obtained from capacitance–voltage (C–V) measurements. We also showed that the recyclic growth process used in this study effectively improves the purity of the epilayers because the mobility at 77 K is enhanced approximately threefold and the ionized carrier concentration decreases threefold compared with their initial values. We also demonstrated that the recyclic growth process is effective in eliminating impurities such as carbon and silicon by analyzing the PL spectra.