Optical and structural characterization of LTG-GaAs correlating excess As with THz emission
Optical and structural characteristics of in-house low-temperature-grown gallium arsenide (LTG-GaAs) grown at different substrate temperature (TS) were investigated to determine their effects in the terahertz (THz) emission of the sample. Arsenic (As)-related defects in LTG-GaAs were shown to reduce the photoluminescence (PL) emission of the samples grown at lower TS. The concentration of excess As atoms in LTG-GAs was calculated from the Raman spectra and was shown to be 1.64% and 2.50% for samples grown at TS = 320°C and 270°C, respectively. The sample with higher concentration of excess As exhibited Raman spectra with narrow full width at half maximum attributed to larger As precipitate by finite particle size effect. The THz emission intensity of LTG-GaAs was observed to be significantly higher than the reference GaAs sample which proved that the presence of excess As in LTG-GaAs was effective in the enhancement of THz radiation.