The explanation of the so-called Auger-like thermal recovery of the EL2 defect in n-type GaAs

Abstract

We present an experimental study of the EL2-defect thermal recovery in n-type GaAs under hydrostatic pressure up to 1.2 GPa. The most characteristic experimental result is the nonmonotonous pressure dependence of the temperature at which the EL2 defect thermally recovers. We solve numerically the equations describing the recovery process, and we prove that in order to explain our experimental data it is absolutely necessary to take into account the existence of the recently discovered acceptorlike level of the metastable EL2. Moreover, we show that the most straightforward explanation of all our experimental results should assume that in n-type GaAs the recovery process always proceeds via the negative-charge state of the metastable EL2. Since our explanation of the recovery process does not require the recovery rate to be directly proportional to the free-electron concentration, the problem of the so-called Auger-like thermal recovery of the EL2 defect in n-type GaAs seems to be finally gone.

Application of the bounds-analysis approach to arsenic and gallium antisite defects in gallium arsenide

“…3 is the supercell-size dependence of the defect level, Our result for the 0 charge state is 0.13 eV lower than the measured activation energy (0.34 eV) for the 0 charge state, 29 and our result for the −1 charge state is 0.025 eV lower than the measured activation energy (0.075 eV) for the −1 charge state. 33 In addition, our result for the 0 charge state is 0.02 eV higher than the activation energy obtained by Schultz and von Lilienfeld using the LDA, 34 and our result for the −1 charge state is close to the estimate of Dabrowski and Scheffler 29 (0 eV) based on an analysis of Kohn-Sham eigenvalues.…”

“…31,32 From experiments, EL2* is known to have two charge states (−1, 0) and one level (−1/0) 0.016 eV above the CBE at ambient pressure. 33 We began our studies of EL2 and EL2* by choosing candidate charge states, calculating their DFT energies and levels (Eq. 1), and performing a bounds analysis on the results.…”

“…In semi-insulating GaAs, it is further observed that neutral EL2* transforms to EL2 with an activation energy of 0.34 eV, 29 while in n-type GaAs, −1 EL2* transforms to EL2 with a lower activation energy of 0.075 eV, emitting an electron to the conduction band. 33 In addition to our calculations for EL2 and EL2*, we used the dimer method 38 to determine the saddle-points for transitions between EL2* and EL2 in the 0 and −1 charge states. The saddle-point calculations were performed using the same supercell sizes and sampling meshes used for stable and metastable EL2 and EL2*.…”

Orientation of Metastable EL2 under Uniaxial Stress

“…It was found moreover that orientation of EL2* centers depended on the method of the EL2-photoquenching [2] which confirmed the attribution of EL2 metastability to the transformation AsG a ↔ VGaΑsi [3,4]. The key role in the thermal recovery of EL2 in n-type GaAs is played by the acceptor level of EL2* ([EL2*]-/0) [5,6] which is orientationally degenerate and split under [111] stress into two components: the triplet ([EL2*]T' -/ 0 ) a n d t h e singlet ([EL2*]s -/ 0 ) s u b l e v e l s . W e p e r f o r m e d t h e e l e c t r i c a l c o n d u c t i v i t y a n d H a l l effect measurements of n-type GaAs in order to investigate the electrical properties of these levels under [111] uniaxial stress.…”