EVALUATION OF SEMICONDUCTOR CRYSTAL

PURPOSE:To evaluate a crystal from the correlation between the photo luminescence PL intensity and LED output by irradiating the light beam in such an intensity and wavelength as generating 5% or more of the carrier density at the time of operation of element to the active layer of semiconductor crystal. CONSTITUTION:When the NdYAG laser in the wavelength of 1.064mum is irradiated to the crystal of In1-xGaxAs1-yPy (0=1)/InP, the n type InGaAsP active layer 3 which is transparent for InP and only the p type InGaAsP connecting layer which is not transparent for InP are excited from the relation between the forbidden energy band width and energy of irradiating light beam. Thereby, an intensity of the combined light beam of PL's of both layers can be obtained. But, when the active layer 3 is thicker than 1mum as in the case of LED, the excited light beam is almost absorbed by the layer 3. Therefore, it is not so different from that obtained when the layer 5 is removed. When 5% of more of carrier density during operation of element is generated by increasing the irradiation energy up to 500W/cm , a favorable correlation between LED output and PL intensity can be obtained, and characteristic of crystal can be forecast before the element processing stage, thereby contributing to the manufacture of element.