ir A. Naz

Electrical characterization of alpha radiation-induced defects in p-GaAs grown by metal-organic chemical-vapor deposition

Investigations of the alpha particle irradiation-induced defects in low-pressure metal-organic chemical-vapor deposition grown p-GaAs have been carried out. By employing deep-level transient spectroscopy, at least seven radiation-induced deep-level defects have been observed in the lower half of the band gap in the temperature range of 12−475 K. Double-correlation deep-level transient spectroscopy measurements show three prominent levels: two known radiation-induced levels namely, Hα1 and Hα5, and one inadvertent center HSA, present before irradiation, to exhibit a significant dependence of thermal emission rate on the junction electric field. For Hα1 and HSA the field-enhanced emission data are well fitted with a Poole-Frenkel model, using a three-dimensional square-well potential with radius r=3.2 and 1.43 nm, respectively. The field effect for Hα5 has been explained by a square-well potential in combination with a phonon-assisted tunneling process. Detailed data on the carrier capture cross section for...

4d transition-metal impurity rhodium in GaAs grown by metal-organic chemical vapor deposition

Deep levels associated with 4d transition-metal impurity rhodium have been investigated in GaAs epitaxial layers grown by metal-organic chemical vapor deposition, using deep level transient spectroscopy (DLTS) technique. A comprehensive study of deep levels in the entire bandgap of GaAs has been carried out using both n- and p-type GaAs crystals over a wide temperature scan range, 12–470 K. In the n-type, Rh-doped material, two prominent broadbands of deep levels are found to be associated with Rh impurity; one in the upper-half and the other in the lower-half bandgap. In addition, one relatively small peak at the high temperature end of the majority-carrier emission spectra, corresponds to a deep level at Ec−0.92 eV, is also detected in the n-type Rh-doped samples. The minority carrier (hole) emission band in n-type material is found to consist of a doublet of hole emitting deep levels, labeled RhA and RhB, in the lower-half bandgap. This doublet is clearly observed to correspond to two Rh-related deep l...

Effects of irradiation and annealing on deep levels in rhodium-doped p-GaAs grown by metal-organic chemical-vapor deposition

This paper reports a detailed study of the effects of irradiation and thermal annealing on deep levels in Rh-doped p-type GaAs grown by low-pressure metal-organic chemical-vapor deposition, using deep level transient spectroscopy (DLTS) technique. It is found upon irradiation with alpha particles that, in addition to the radiation-induced defect peaks, all the Rh-related peaks observed in majority, as well as minority-carrier emission DLTS scans show an increase in their respective concentrations. The usually observed α-induced defects Hα1, Hα2, and Hα3 are found to have lower introduction rates in Rh-doped samples, as compared to reference samples (not doped with Rh). Alpha-irradiation has been found to decompose the two minority carrier emitting bands (one at low temperature ∼150 K and the other at ∼380 K) observed prior to irradiation into distinct peaks corresponding to deep levels Rh1 and Rh2 and EL2 and Rh3, respectively. A similar effect is also observed for the majority-carrier emitting band compo...