An optical and electrical relaxation oscillator using a Si homojunction structured light emitting diode

We propose an optical and electrical relaxation oscillator making use of an S-shaped negative resistance characteristic of a recently developed light-emitting diode using a bulk silicon crystal homojunction. From simulations, we found that the voltage and optical power oscillated synchronously, and their oscillation frequency increased with increasing injection current. The synchronous oscillation was also confirmed by experimental measurements. The amplitude of the voltage was 50?V_p-p, the amplitude of the optical power was 3?mW_p-p, and the maximum oscillation frequency was 34?kHz. The measured value of the spontaneous emission lifetime of a Si wafer was 900?ps, which was as short as that of direct transition-type semiconductors.