Hg1-x CdxTe mid-wavelength infrared (MWIR) avalanche photodiode (APD) grown on Si substrate

Photodetectors with high bandwidth and internal gain are required to detect highly attenuated optical signals for defense application and long distance communication. IR avalanche photodiodes (APDs) are best suited for this purpose due to their internal gain-bandwidth characteristics coupled with long range data transmission capability. For the past two decades, HgCdTe has been the most successful material for infrared photodetector applications. Recent advances in epitaxial growth techniques made possible the growth of advanced HgCdTe APD structures, but to the best of our knowledge all are grown on expensive substrates (e.g. CdZnTe, CdTe). We report for the first time HgCdTe-based MWIR (4.5 μm) p-i-n APD grown on Si substrate by molecular beam epitaxy (MBE). The devices were fabricated by 365nm UV photolithography and wet-etching technique. The diode had a junction area of 300μm diameter. The R0A of the diode was 3 x 106 Ω-cm2 at 77K. Multiplication gains of 800 were measured at a reverse bias of 10 V in the linear operation regime. The gain increased exponentially as the reverse bias was increased, indicating that only one carrier is responsible for the impact ionization. Temperature dependence of the multiplication gain and of the breakdown voltage further confirms that avalanche multiplication dominates high reverse bias I-V characteristics.