Investigation of deep level defects in electron irradiated indium arsenide quantum dots embedded in a gallium arsenide matrix

Abstract

Gallium arsenide diodes with and without indium arsenide quantum dots were electron irradiated to investigate radiation induced defects. Baseline and quantum dot gallium arsenide pn-junction diodes were characterized by capacitance–voltage measurements, and deep level transient spectroscopy. Carrier accumulation was observed in the gallium arsenide quantum dot sample at the designed depth for the quantum dots via capacitance–voltage measurements. Prior to irradiation, a defect 0.84eV below the conduction band (EC – 0.84eV) was observed in the baseline sample which is consistent with the native EL2 defect seen in gallium arsenide. After 1MeV electron irradiation three new defects were observed in the baseline sample, labeled as E3 (EC – 0.25eV), E4 (EC – 0.55eV), and E5 (EC – 0.76eV), consistent with literature reports of electron irradiated gallium arsenide. Prior to irradiation, the addition of quantum dots appeared to have introduced defect levels at EC – 0.21, EC – 0.38, and EC – 0.75eV denoted as QD–DX1, QD–DX2, and QD–EL2 respectively. In the quantum dot sample after 1MeV electron irradiation, QD–E3 (EC – 0.28eV), QD–E4 (EC – 0.49eV), and QD–EL2 (EC – 0.72eV) defects, similar to the baseline sample, were observed, although the trap density was dissimilar to that of the baseline sample. The quantum dot sample showed a higher density of the QD–E4 defect and a lower density of QD–E3, while the QD–EL2 defect seemed to be unaffected by electron irradiation. These findings suggest that the quantum dot sample may be more radiation tolerant to the E3 defect as compared to the baseline sample.