LOW-FREQUENCY NOISE STUDIES OF ALAS - GAAS - ALAS QUANTUM-WELL DIODES AT 77-K

The low frequency noise of AlAs-GaAs-AIAs quantum well diodes (QWD) was measured at both 77 and 300 K. The experimental results show that, in the frequency range from 2 Hz to a few kHz, the noise is almost-equal-to 1/f at both temperatures. At room temperature, the current noise spectrum S(I)(f) in A2 Hz-1 is proportional to the square of the current through the QWD. However, the noise spectral density at 77 K was not proportional to the square of the current. At 300 K, S(I)(f)/I2 versus bias voltage is fairly flat up to the negative differential resistance (NDR) region, but beyond the NDR region, a small jump in S(I)(f)/I2 of a few dB was observed. This increase in S(I)(f)/I2 beyond the NDR region was found to be almost-equal-to 20 dB continuous increase at 77 K. The results also show that below the NDR region, the noise levels are about the same at both 300 and 77 K. However, the noise increases more at 77 K than at 300 K as the bias voltage increases beyond the NDR region.