Growth and fabrication issues of GaSb based detectors
Antimony based semiconducting materials are of great interest to the research and technology development communities for mid and long infrared applications. In particular, the antimony based detector is a key component in advanced high speed and low noise optical receiver systems. However, the growth and fabrication of antimony based detectors face several challenges, of which, the most important is the reduction of surface leakage which severely limits their performance. In this paper, a review of the current growth techniques (liquid phase epitaxy LPE, chemical vapor deposition CVD or molecular beam epitaxy MBE) for antimony based devices is presented. The metamorphic growth technique is also discussed because it allows a device designer to use any conventional starting wafer and then to subsequently grow layers of arbitrary composition of antimony containing alloys that allows for changing the detection wavelength of interest. However, since surface leakage severely limits the detector's performance, then suitable techniques to passivate and neutralize the reactive GaSb surface, and also to finally encapsulate the detectors are required. This reduction of the leakage currents will lead to detectors having higher detectivity and efficiency. Further, avalanche photodetectors with gain can be designed using antimonide based materials if the processing steps can be optimized. Therefore, in this paper, we also present an up to date review of the available techniques for reducing surface leakage. This includes neutralizing the exposed side walls using sulfur passivation and/or by depositing another semiconducting layer using either MBE regrowth or chemical deposition. Finally, antimony based detectors are reviewed and their detectivity, zero bias resistance area product and surface resistivity are compared.