Optical assessment of the main electron trap in bulk semi-insulating GaAs

Abstract

Near-infrared optical absorption in undoped bulk GaAs ingots is shown to be due essentially to the presence of the main deep donor EL2. Measurement of the corresponding absorption represents the first known method of quantitative determination of that level in semi-insulating material. Furthermore, complete quenching of the corresponding absorption is shown to occur under high intensity illumination. This strong effect, reported for the first time, can be directly related to the existence of a metastable state for the level EL2 presenting a strong lattice relaxation.

Investigation of Device and Electronic Interactions Associated with GaAs Device Processing.

“…8a. This optical quenching has not as yet been adequately explained or understood; yet it has been taken as the "EL2" fingerprint, [29] i.e., a unique criterion for the identication of EL2. This interesting concept of "EL2 fingerprinting" was subsequently stretched far beyond its original ramifications.…”

“…8 is a characteristic feature of ntype and semi-insulatinq GaAs [29). This structure is related to EL2.…”

“…*In an earlier study [47] employing simplified correction factors we have also underestimated the values of NT which were much closer to those of ref. 29. Since 1977 EL2 has been known to exhibit optical quenching [52,27] which transfers the level into a nmtastable state resulting in quenching of the corresponding photocapacitance, and to the bleaching of the characteristic EL2 optical absorption, [28] as shown in Fig.…”

Acoustoelectrical Relaxation in GaAs by the Formation and the Recovery of Metastable EL2

“…Thus, very little is known about this metastable state, and only the transitions between the two states have been investigated. Techniques like photoconductivity [8], infrared absorption [9], and photocapacitance [6] have been applied to study the transformation. In this paper we present another experimental method, based on the acoustoelectrical relaxation of conduction electrons screening the piezoelectrical field of harmonically strained GaAs crystals.…”

EL2-related studies in irradiated and implanted GaAs

“…23 (1988) [1][2][3] -under a low-temperature photoexcitation it transforms into a different configuration, EL2 has been extensively studied for the past five years and its properties have been the subject of several recent review papers [4][5][6][7]. As a final result, this metastability which manifests by photoquenching behaviour of photocapacitance [3], photoconductivity [8], electron paramagnetic resonance (EPR) [9], photoluminescence and optical absorption [10,11] has become a kind of specific fingerprint for the presence of EL2.…”