Controlled Dislocations Injection in N/P Hg1−xCdxTe Photodiodes by Indentations

Abstract

HgCdTe (MCT) is a widely used semiconductor material used for manufacturing high-quality infrared detectors. At Sofradir, HgCdTe is grown by liquid phase epitaxy on lattice-matched CdZnTe substrates. Low threading dislocation densities (TDD) in the low 1 × 104 dislocations/cm2 are routinely obtained. Despite these low TDD levels, these dislocations are known to affect the electrical properties of photodiodes. Dislocation electrical behavior needs a deeper understanding in order to improve the manufacturing technology and the photodiode performance. In this study, we use Vickers micro-indentations to inject extra dislocations into dedicated areas of n on p mid-wave infrared photodiodes. The photodiodes were then characterized and analyzed theoretically thanks to I(V) and I(t) measurements under F/3 flux conditions (typical focal plane array illumination) at 110 K. Microindentations were performed close to the photodiodes in order to inject controlled high to very high dislocation densities. The effect of such an injection was then studied in depth on photodiodes. The electrical results have shown that the temporal variation of the current I(t) is mostly affected by the generation of extra dislocations. The same type of degradation of I(t) was observed in focal plane arrays, which confirms that dislocations play an important role in the generation of noise defects.