High performance SWIR HgCdTe detector arrays

Abstract

Short wave infrared (SWIR) devices have been fabricated using Rockwell's double layer planar heterostructure (DLPH) architecture with arsenic-ion implanted junctions. Molecular beam epitaxially grown HgCdTe/CdZnTe multilayer structures allowed the thin, tailored device geometries (typical active layer thickness was -3.5 Mm and cap layer thickness was -0.4 Mm) to be grown. A planar-mesa geometry that preserved the passivation advantages of the DLPH structure with enhanced optical collection improved the performance. Test detectors showed Band 7 detectors performing near the radiative limit (-3-5X below theory). Band 5 detector performance was -4-50X lower than radiative limited performance, apparently due to Shockley-Hall-Read recombination. We have fabricated SWIR HgCdTe 256 x 12 x 2 arrays of 45 ~tm x 45 ~m detector on 45 pm x 60 ~m centers and with cutoff wavelength which allows coverage of the Landsat Band 5 (1.5-1.75 ~tm) and Landsat Band 7 (2.08-2.35 Mm) spectral regions. The hybridizable arrays have four subarrays, each having a different detector architecture. One of the Band 7 hybrids has demonstrated performance approaching the radiative theoretical limit for temperatures from 250 to 295K, consistent with test results. D* performance at 250K of the best subarray was high, with an operability of -99% at 101~ cm Hz'2/W at a few mV bias. We have observed 1/f noise below 8E-17 AHz -1/2 at 1 Hz. Also for Band 7 test structures, Ge thin film diffractive microlenses fabricated directly on the back side of the CdZnTe substrate showed the ability to increase the effective collection area of small (nominally <20 Mm pm) planar-mesa diodes to the microlens size of 48 ~tm. Using microlenses allows array performance to exceed 1-D theory up to a factor of 5.

Performance limitation of short wavelength infrared InGaAs and HgCdTe photodiodes

“…5,6 Recently, double layer planar heterojunction (DLPH) p-on-n photodiodes in molecular beam epitaxy (MBE) HgCdTe on CdZnTe substrates have been elaborated by As-ion implantation and the p-dopant activation by an open-tube Hg anneal. 7 The goal of this paper is comparing the ultimate-tonoise performance of InGaAs and HgCdTe photodiodes operated in the 1.5-3.7 µm spectral range. Results of theoretical predictions are compared with lems; excess thermal generation results in increased dark current and recombination which reduces photocurrent.…”

Design Principles for High QE HgCdTe Infrared Photodetectors for eSWIR Applications

“…40 On the other hand, the reported SRH lifetime in In-doped, MBE grown n-type absorber layers is in the order of ~ 1 μs. [40][41][42][43] The direct experimental comparison of n-on-p and p-on-n photodetectors operating in the eSWIR band with cut-off wavelength of 2 μm has been undertaken by CEA-LETI in France on a vacancy doped p-type absorber (grown by LPE) and on In-doped n-type absorber (grown by MBE). The results show a similar quantum efficiency for both technologies.…”

Narrow bandgap HgCdTe technology for IR sensing and imaging focal plane arrays

“…In addition, as shown in Figure 6, it can be observed that the internal QE strongly depends on the SRH lifetime of the minority carriers. While there is a significant lack of reported data on the minority carrier lifetime in absorber layers with composition suitable for operation in the eSWIR waveband, a recent report indicates minority electron lifetime in the 30-50 ns range for Hg-vacancy doped Hg0.62Cd0.38Te heteroepitaxially grown by MBE on Si substrates [12], whereas the SRH-limited minority hole lifetime in extrinsic n-type doped epilayers is typically of the order of 1 μs [12][13][14]. Based on preliminary results presented below, the electron minority carrier lifetime in Hg0.51Cd0.49Te grown by MBE on CdZnTe substrates is estimated to significantly exceed 50 ns.…”