Microscopic nature of thermally stimulated current and electrical compensation in semi-insulating GaAs

Abstract

In this work undoped semi-insulating ͑SI͒ GaAs grown by vertical gradient freeze and liquid encapsulated Czochralski methods was studied by near-infrared absorption ͑NIRA͒, thermally stimulated current ͑TSC͒ and positron annihilation techniques. The positron experiments reveal both gallium and arsenic vacancies, as well as gallium and arsenic antisites, in the samples. By comparing the results from the TSC and positron measurements, the following relations are found in the defect concentrations: trap T 2 correlates with the arsenic antisite and trap T 5 with the arsenic vacancy. The ionized fraction of the arsenic-antisite-related EL2 defect is obtained from NIRA measurements. The positive charge of these ionized EL2 defects correlates with the net negative charge, 3͓V Ga 3Ϫ ͔ϩ2͓Ga As 2Ϫ ͔Ϫ͓V As ϩ ͔, related to the gallium vacancies and antisites and arsenic vacancies detected in positron measurements. The intrinsic defects may thus contribute significantly to the electrical compensation in SI GaAs.

Thermally stimulated current spectroscopy on silicon planar-doped GaAs samples

“…1 Until now, almost all the studies have been concerned with samples without any structural detail, which means that they can hardly be used to simulate real devices. [2][3][4][5][6][7] In this study we have used thermally stimulated current ͑TSC͒ spectroscopy 8 to identify deep traps present in LTG MBE-GaAs epilayers having a silicon planar-doped layer. The V-shaped potential well produced by the silicon-ionized donors confines the free electrons in sub-bands in the neighborhood of the silicon-doped layer producing a quasibidimensional ͑2D͒ electron gas, and it is important in defining the electrical and optical properties of the sample.…”

Deep centers in undoped semi-insulating InP

“…5,6 Although the application of the TSC technique to Fe-doped InP has revealed at least six traps in the range 80 to 250K, 7-9 the connection of these deep centers with particular point defects in SI InP is still not clear. 5,6 Although the application of the TSC technique to Fe-doped InP has revealed at least six traps in the range 80 to 250K, 7-9 the connection of these deep centers with particular point defects in SI InP is still not clear.…”

Activation energies of the EL6 trap and of the 0.15 eV donor and their correlation in GaAs

“…In the literature different models exist. Some authors correlate EL6 and also the 0.15 eV donor (TDH) with an As-vacancy complex [24,25]. An As vacancy as a constituent of the EL6 defect has been clearly proved by positron annihilation [25].…”