High speed low noise InAs electron avalanche photodiodes for telecommunication and infrared sensing applications

The leakage current, avalanche gain, excess noise and frequency response of InAs avalanche photodiodes (APDs) were investigated. Despite having a narrow bandgap, InAs APDs, which were fabricated using optimized fabrication procedures and surface passivation technique, were able to provide reasonably low leakage current for practical applications. The exponentially rising avalanche gain with increasing bias voltage without a classical avalanche breakdown exhibited its electron-dominated impact ionization characteristic and avalanche gain as high as 165 was measured. The excess noise or avalanche noise was found to be independent of gain and temperature with the excess noise factors fluctuating between 1.45 and 1.6 at high gain. The 3-dB bandwidth of InAs APDs was determined to be ~ 3.5 - 4 GHz and it was highly possible that the surface passivation dielectric and the unavailability of a lattice-matched semi-insulating substrate were the major limiting factors. However, unlike other mature APDs technologies, the 3-dB bandwidth of InAs APDs remained constant even up to the highest achievable avalanche gain, providing a record high gain-bandwidth product of ~ 580 GHz.