Design of InGaN based photodiodes by internal field engineering

In this paper, the role of piezoelectric fields on the performance of multiple-quantum-well based PIN photodetectors is studied. It is shown that the responsivity critically depends, through the effect of piezoelectric fields, on the growth sequence starting either from an n-type substrate (standard PIN) or from a p-type substrate (inverted PIN). Piezoelectric fields and junction built-in fields are aligned in the inverted PIN structure, thus increasing the collection efficiency as shown from theoretical calculations. In contrast to the blueshift found in the photoresponse of standard PIN structures, the inverted PIN structures exhibited a redshifted with increasing reverse voltage. Three different photodetector structures have been designed, grown, processed and characterized. Doping levels and barrier dimensions have also been engineered to improve the detector responsivity.