Optical Photogenerated Traps in Semi-Insulating GaAs Bulk Material

The photogeneration of traps in semiinsulating GaAs bulk material under YAG excitation is reported. The samples used in the experiment were wafers 400 millimicrons thick and were resistive to room temperature at a level between 10 to the 8th and 10 to the 9th ohm-cm. The experimental setup for measuring the photocurrent was similar to that used in Thermal Stimulated Current (TSC) experiments. Photogeneration was recorded following YAG laser excitation and had a photoconductivity of 1.42 eV. From the results of the experiment, it is shown that an intense excitation by YAG laser can generate new traps which are responsible for photocurrent enhancement as well as the varying distribution of traps in TSC. Diagrams illustrating the typical TSC spectra and the variation of the photo-current with temperature at 1.42 eV with and without laser excitation are provided.