Characterization of semi-insulating GaAs:Cr by means of DC-CPM technique

Abstract

In the present paper, constant photocurrent method, ‘CPM’ is used to determine the defects distribution from the optical absorption spectra of semi-insulating Cr-doped GaAs. By using the derivative method, we have extracted the distribution of the density of states DOS close to valence band edge Ev from the measured optical absorption spectrum. We have also developed a computer code program dc-CPM which have been used to compute the total absorption spectrum and their components using a model density of states inferred from two complementary techniques: constant photocurrent method, ‘CPM’ and transient photocurrent ‘TPC’. It is found that by combination of the two measurement techniques ‘CPM’ and ‘TPC’, and the two absorption spectra components and , we are able to have a full reconstruction of the density of states distribution below and above the Fermi level for such materials.

Keywords

• constant photocurrent method
• transient photocurrent
• optical absorption spectrum
• gallium arsenide, defect states