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.
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