Identification of a vanadium-related level in liquid encapsulated Czochralski-grown GaAs

Abstract

We present the first positive identification of a vanadium-related electron trap in V-doped GaAs crystals grown by the liquid encapsulated Czochralski technique in pyrolytic boron nitride crucibles. Detailed deep level transient spectroscopy and capacitance transient analysis yielded a trap energy of 0.15±0.01 eV below the conduction band and an electron capture cross section of about 2×10−14 cm2. Optical absorption and mobility data show that this level corresponds to the ionized acceptor state V2+(3d3) of substitutional vanadium. No midgap levels other than EL2 could be detected in these V-doped crystals showing that doping with vanadium plays no direct role in the compensation process in semi-insulating GaAs crystals.

A study of deep levels in vanadium-doped GaAs grown by OMVPE

“…There are still a number of questions regarding the understanding of optical and electrical properties of vanadiumdoped GaAs (GaAs:V). No mid gap level related to the isolated vanadium impurity (V) has been found which can explain the fact that this material is semi-insulating (SI) [1]. In [2,3] it was reported that the role of V is to decrease the shallow donor concentration below the acceptor concentration and consequently to fulfill the necessary condition for achieving SI GaAs with a compensation mechanism based on the native EL2 midgap donor, omnipresent in melt-grown GaAs.…”

“…It is well established that V doping of GaAs introduces an acceptor level attributed to the V 3+ /V 2+ transition, at 0.15 eV below the conduction band (E c ) [1,2,12,13]. However, GaAs:V grown by the Horizontal Bridgman method presented a deeper electron trap at E c -0.22 eV.…”

Photoluminescence Excitation Spectroscopy of MOCVD-Grown: GaAs:V

“…It has been shown that vanadium gives rise to a deep acceptor level at Ec -0.15 eV [2,3,4]. Figure 1 shows the substitutional vanadium levels in GaAs [4].…”