Avalanche mechanism in p+-n--n+ and p+-n mid-wavelength infrared Hg1-xCdxTe diodes on Si substrates

Hg1-xCdxTe mid-wavelength infrared (MWIR) p(+)-n(-)-n(+) and p(+)-n(-) avalanche photodiodes (APDs) with a cut-off of 4.9 mu m at 80 K were fabricated on Si substrates. Diode characteristics, avalanche characteristics, and excess noise characteristics were measured on two devices. Temperature-dependent diode and avalanche characterization was performed. Maximum 3 x 10(6) Omega cm(2) and 9 10(5) cm(2) zero-bias resistance times active area (R-0 A) products were measured for the p(+)-n(-)-n and p(+)-n devices at 77 K, respectively. Multiplication gains of 1250 and 410 were measured at -10 and -4 V for the p(+)-n(-)-n(+) and p(+)-n APDs at 77 K, respectively, in the front-illumination mode with the help of a laser with an incident wavelength of 632 nm. The gains reduce to 200 and 50 at 120 K, respectively. The excess noise factor in all APDs was measured to be in the range of 1 to 1.2.