Absolute pressure dependence of the second ionization level of EL2 in GaAs

Abstract

We report the results of deep level transient spectroscopy experiments with the second ionization level of the double donor defect (EL2) under uniaxial stress in p-type GaAs. We measure the shift in the hole emission rate as a function of stress applied in the [100] and [110] directions. By modeling the valence band with two independently displacing bands and appropriately derived effective masses, we determine the absolute hydrostatic pressure derivative of the defect to be 39±15 meV GPa−1. The shear contribution is negligible. These results are very different from those obtained for the first ionization level, which has a much higher absolute pressure derivative of 90 meV GPa−1.

Breathing-mode relaxation associated with electron emission and capture processes ofEL2 in GaAs

“…The various pressure derivatives and A^^are summarized in Table I. [7]. Analysis of the results, based on the use of -0.7 ± 1.0 eV (which is very close to the value deduced in Ref.…”

“…For the ( + /+ + ) level, the experiment of Bliss et al [7] on p-type GaAs examined hole emission, and, to emphasize this point, we designate the transition as (++/+) in Table I. The absolute pressure shift of this level is positive, implying that the level moves up in the gap relative to the lower-lying reference state which is the valence-band edge.…”

“…The second level corresponds to the second donor ionization state (-l-/-f + ) and is observed in p-type GaAs. It has a hole emission activation energy of 0.54 eV and, presumably, no capture barrier [7], so that it is located at £",,4-0.54 eV (where £",, is the valence-band edge).Although the preponderance of the evidence definitively points to the involvement of the As antisite defect (ASGU) in its stable configuration, uncertainties still remain as to EL2\ exact microstructure. Currently, the two leading models [1-6] associate EL2 with either (i) the isolated Asca or (ii) a loosely bound As-antisite-Asinterstitial (i.e., Asoa-As,) pair.…”

“…The second level corresponds to the second donor ionization state (-l-/-f + ) and is observed in p-type GaAs. It has a hole emission activation energy of 0.54 eV and, presumably, no capture barrier [7], so that it is located at £",,4-0.54 eV (where £",, is the valence-band edge).…”

Defect studies in low-temperature-grown GaAs

“…The second ionization level of EL2 has been identified with this technique and lies at 0.52 eV (Baeumler, ·et al 1985). Specially prepared p-type samples which also contain EL2 have made it possible to study the second ionization level by DLTS (Bliss, et al 1990;Lagowski, et al 1985).…”