InGaAs/InP PIN photodetector arrays made by MOCVD based zinc diffusion processes

InGaAs based long-wavelength near infrared detector arrays are very important for high dynamic range imaging operations seamlessly from daylight environments to dark environments. These detector devices are usually made by open-hole diffusion technique which has the advantage of lower leakage current and higher reliability. The diffusion process is usually done in a sealed quartz ampoule with dopant compounds like ZnP2, ZnAs3, CdP2 etc. side by side with semiconductor samples. The ampoule needs to be prepared and sealing process needs to be done in very clean environment and each time can have variations. In this work we demonstrated using MOCVD growth chamber to perform the diffusion process. The advantages of such a process are that the tool is constantly kept in ultra clean environment and can reproducibly provide clean processes without introducing unexpected defects. We can independently control the temperature and flow rate of the dopant - they are not linked as in the ampoule diffusion case. The process can be done on full wafers with good uniformity through substrate rotation, which is good for large detector array fabrications. We have fabricated different types of InGaAs/InP detector arrays using dimethyl zinc as the dopant source and PH3 or AsH3 for surface protection. Pre-studies of Zn-diffusion profiles in InGaAs and InP at different temperatures, flow rates, diffusion times and followed annealing times were conducted to obtain good control of the process. Grown samples were measured by C-V profilometer to evaluate the diffusion depth and doping concentration. The dependence of the diffusion profile with temperature, dopant partial pressures, and annealing temperature and time and some of the fabricated device characteristics are reported.