Recovery from the Metastable EL2 Defect in GaAs Under Monochromatic Light Illumination.
- PDF / 314,095 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 22 Downloads / 186 Views
RECOVERY FROM THE METASTABLE EL2 DEFECT IN GaAs UNDER MONOCHROMATIC LIGHT ILLUMINATION. M. 0. MANASREH* and D. W. FISCHER** *Electronic Technology Laboratory (WRDC/ELRA), Wright Research and Development Center, Wright-Patterson Air Force Base, Ohio 45433-6543 **Materials Laboratory (WRDC/MLPO), Wright Research and Development Center, WrightPatterson Air Force Base, Ohio 45433-6533.
ABSTRACT The infrared absorption technique is used to study the recovery of the EL2 metastable state in semi-insulating GaAs under monochromatic light illumination. The induced optical recovery is monitored after low intensity (< 2mW/cm 2) irradiation in the energy range 0.7 < hv < 1.5 eV. The data exhibit a complex structure consisting of a broad band around 0.9 eV and a set of multiple sharp peaks between 1.44 and 1.5 eV. This recovery is strongly dependent on the sample, temperature and illumination time. The present results suggest that a) the existing data and theoretical predictions for the isolated ASGa antisite structure are not compatable with the optical recovery data, b) EL2 is affected dramatically by other defects (traps) present in the sample and c) the peaks observed in the optical recovery data are coincident with the arsenic vacancy energy levels and therefore the present results support the proposed complex models involving an arsenic vacancy.
INTRODUCTION The atomic structure of the mid-gap defect known as EL2 in GaAs and how its constituent atom(s) rearrange during the transformation of this defect from the normal state (EL2o) to the metastable configuration (EL2*) in response to photo-excitation at low temperatures (T 5 100 K) are issues which have initiated some very active controversies in recent years. The
presence of an optically induced metastable configuration is the most unusual aspect of this
defect. The key to reaching a clearer understanding of the nature of the EL2 defect is therefore to understand its metastable state which apparently exhibits no experimentally observed properties of its own. A few attempts have been made recently to transform the EL2 defect from EL2* to EL20 by photon irradiation. Such photo-induced recovery has been reported for photoluminescence 1 , photoconductivity 2, photocapacitance 3, infrared(IR) absorption 4 -7 , and electron paramagnetic resonance 8 (EPR). Even though all these studies have established that the optical recovery from EL2* can be induced, they disagree on some important aspects such as the amount of optical recovery and the spectral dependence of the recovery. In this article we present photo-induced recovery properties of the EL2 defect. Optical recovery from EL2* was found to be sample dependent indicating the existence of interactions
between EL2 and other defects and traps present in the samples. The current results will be tested against the isolated arsenic antisite model as well as other more complex models. The recovery data are in good agreement with the calculated arsenic vacancy energy levels lending support to models containing this point defect.
Data Loading...
