B. L. Sharma

Engineering Interface Composition for Passivation of HgCdTe Photodiodes

A compositionally graded surface layer has been created for the passivation of Hg1-xCdxTe photodiodes. The graded CdTe-Hg1-xCdxTe interface was created by deposition of CdTe and subsequent annealing. It was found that the composition gradient and width of the graded region could be tailored by adopting a suitable annealing procedure. The effect of grading on the interface electrical properties and photoelectrical properties was studied by X-ray photoelectron spectroscopy (XPS), photoconductive decay, and C-V measurements. Insulator fixed-charge density and interface-trap density could be reduced to 3times1010 cm -2 and 2times1010 cm-2middoteV-1, respectively, by creating a graded interfacial composition. The interface conditions so engineered led to a low surface recombination velocity ~3000 cm/s. A direct correlation has been established between the process conditions, interfacial composition, and the electrical/photoelectrical properties of the CdTe-Hg1-xCdxTe heterostructures. The passivation layer formed by this method is shown to be suitable for the fabrication of high-performance infrared detectors

Effect of HgCdTe–passivant interface properties on the responsivity performance of photoconductive detectors

Abstract The variations in the responsivity, minority carrier lifetime and shunt resistance (arising due to surface accumulation) have been measured as a function of the gate potential in a HgCdTe gated photoconductor test structure. The measured variations have been shown to be in very good agreement with our model previously published. It is predicted that the optimisation of the trap density and fixed charges at the HgCdTe–passivant interface can lead to improvements in the response uniformity of the detector elements in an array.

Observation of Over-Layer Deposition on HgCdTe Epilayers Grown by Vertical dipping Liquid Phase Epitaxy

The HRXRD and FTIR characterization of HgCdTe epilayers grown by vertical Dipping Liquid Phase Epitaxy was analyzed to indicate the presence of <2 μm low-x HgCdTe over layer. A higher angle shoulder in HRXRD rocking curve and a graded cut-on as well as a double fringe pattern in FTIR was observed. Removal of ~2 μm surface layer by chemical etching improved the FTIR and HRXRD curves.