Abstract

Avalanche photodiodes (APDs) with high speed, high quantum efficiency, low dark current and low multiplication noise are very important in long-haul, high-bit-rate fiber optic communication systems. Operation at the telecommunication wavelength of 1.3|im is a useful attribute. Traditionally, InP-based materials such as InGaAsP have been utilized at this wavelength. However, there are drawbacks for InP-based devices as compared to those fabricated on GaAs substrates. For example, InP wafers are much more expensive than GaAs. In addition, devices on GaAs substrates will benefit from their compatibility with the more advanced GaAs-based electronic technology. Since there are no naturally available material systems lattice-matched on GaAs that can absorb light at 1.3|J.m, in recent years, significant efforts have been devoted to achieve 1.3μm absorption on GaAs substrates. The approaches include InGaNAs alloys, (Ga)InAs quantum dots (QDs) and wafer bonding between GaAs substrates and InGaAsP active layers. An alternative choice is GaAsSb alloy grown on GaAs substrate with high compressive strain. The easy incorporation of an arbitrary amount of Sb into GaAs makes GaAsSb a promising material system. We have reported a GaAsSb resonant-cavity-enhanced (RCE) p-i-n photodiode operating at 1.3μm with 54% external quantum efficiency but high dark current near breakdown [1]. It is known that the separation of absorption and highfield multiplication regions by a thin uniformly doped charge layer, the SACM structure, can significantly lower down the dark current [2]. It has also been reported that a thin AlxGa_1−xAs multiplication region with high Al concentration (x>0.8) can result in very low multiplication noise [3]. To date, however, this type of very low noise multiplication region has not been incorporated into a SACM APD. In this paper, we demonstrate a RCE GaAsSb SACM APD that exhibited much lower dark current than the p-i-n structure and also very low multiplication noise.

© 2002 Optical Society of America