Applications of the Infrared Measurement Analyzer: Hydrogenated LWIR HgCdTe Detectors

Low-cost silicon-based alternative substrates are an attractive choice for next-generation large-area high-resolution multicolor infrared (IR) detector arrays. However, the high density of dislocations formed during molecular-beam epitaxy growth of HgCdTe/CdTe/Si limits the performance of IR arrays, especially in the long-wavelength infrared (LWIR) region. Atomic hydrogen introduced by inductively coupled plasma (ICP) into HgCdTe is expected to passivate dislocations, bulk and surface defects, removing their contributions to dark current. Passivation using ICP hydrogenation can have different effects on HgCdTe photodiode performance, depending on which class of defects is being passivated. The infrared measurement analyzer (IRMA) was used to deconvolute the effects of hydrogenation on LWIR HgCdTe photodiodes through a reverse-modeling fit of the current–voltage (I–V) characteristic. This approach results in a fit with fewer false minima, low parameter error and bias, and high confidence in extracted device parameters. A description of this tool and its application to hydrogenated HgCdTe LWIR detectors is presented. Lower dark currents have been observed after hydrogenation of fully fabricated devices. Model-fits performed on a wide variety of LWIR HgCdTe photodiodes suggest that hydrogenation provides both surface and bulk quality improvements. These benefits of ICP hydrogenation have been retained over several months.