This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detectortechnology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth,device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTeinfrared detectortechnology.

Progress, challenges, and opportunities for HgCdTe infrared materials and detectors

The authors review the current status of minority carrier lifetime in n-type and p-type (Hg, Cd)Te. This review includes a discussion of the relevant (Hg, Cd)Te recombination mechanisms and measurement techniques. The reported experimentally determined lifetimes were related to (Hg, Cd)Te material properties of carrier concentration, Shockley-Read-Hall centres, non-uniformities and dislocation densities.

https://iopscience.iop.org/article/10.1088/0268-1242/8/6S/005/pdf

Minority carrier lifetime in mercury cadmium telluride

Intrinsic infrared detectors

The recombination mechanisms in HgCdTe are analyzed. Detailed expressions for the radiative lifetime are presented, taking into account recent measurements of the absorption coefficient. In p‐type material, carrier freezeout is shown to increase the lifetime exponentially for the radiative and the Auger processes at low temperatures. The effect of background flux is introduced, taking into account its variation with temperature due to the change in energy gap. Lifetime measurements on p‐type samples are in good agreement with combined Auger 7 and radiative mechanisms, where the Auger process is more effective for low x values. Highly compensated materials are dominated by the Shockley–Read recombination. For all samples, the intrinsic region is controlled entirely by the Auger process.

Recombination mechanisms in p-type HgCdTe: Freezeout and background flux effects

The authors review those characterization techniques that have played significant roles in the development of HgCdTe infrared detector technology. They focus on the two specific HgCdTe devices that have achieved widespread application for infrared detection in the LWIR (8-12 mu m) and VLWIR (12-20 mu m) spectral regions: the simple n-type photoconductor and the P-on-n LPE heterojunction photodiode. They review the device physics of these two detectors, relate device performance to starting material properties and processing parameters, and describe the most important characterization techniques that have had a role in their development.

https://iopscience.iop.org/article/10.1088/0268-1242/8/6S/003/pdf

The impact of characterization techniques on HgCdTe infrared detector technology

A new contactless optical modulation technique for the determination of photogenerated carrier lifetimes in semiconductors is presented. The technique consists of measuring the modulation in the transmitted intensity of a dc probe beam (h/ω<Eg) due to a modulated pump beam (h/ω≳Eg). The fractional change in the probe beam transmission is proportional to the excess carrier lifetime. Data are presented for lifetimes of 0.1–4 μ sec measured by this technique in p‐type and near‐intrinsic Hg0.7Cd0.3Te samples at 300 K.

Lifetime measurement in Hg0.7Cd0.3Te by population modulation

The lifetime of excess photogenerated carriers has been measured as a function of temperature and carrier concentration in p‐type Hg0.68Cd0.32Te by contactless optical modulation spectroscopy. An excess carrier lifetime related to impurity substitution on ionized Hg sites is suggested as the dominant Shockley–Read recombination mechanism observed in this material.

Hg vacancy related lifetime in Hg0.68Cd0.32Te by optical modulation spectroscopy

We have applied the technique of optical modulation spectroscopy to the narrow‐gap semiconductor Hg1−xCdxTe. This technique consists of measuring the change ΔIp in the transmitted intensity Ip of a tunable dc probe beam (with photon energy h/ωP<Eg ) due to a fixed‐wavelength chopped pump beam (with photon energy h/ωP≳Eg ). The ΔIp/Ip vs h/ωp spectra were measured for liquid phase epitaxial Hg1−xCdxTe samples at 94 K with x≅0.24–0.37. All spectra show three distinct peaks. The strongest peak occurs near Eg. The other two peaks are relatively sharp and occur below Eg. The energies of these two peaks are close to those of deep levels in Hg1−xCdxTe as recently determined by other techniques. This optical modulation technique, which is relatively simple, contactless, and nondestructive, may have significant potential for high‐sensitivity and high‐resolution study of deep levels in semiconductors.

D. L. Polla

Papers

Lifetime measurement in Hg0.7Cd0.3Te by population modulation

Hg vacancy related lifetime in Hg0.68Cd0.32Te by optical modulation spectroscopy

Observation of deep levels in Hg1−xCdxTe with optical modulation spectroscopy