M. Zandian

Planar p‐on‐n HgCdTe heterostructure photovoltaic detectors

We report a process to fabricate planar Hg1−yCdyTe/Hg1−xCdxTe (x<y) heterostructure photodiodes with the p‐on‐n configuration. The material used for this demonstration was grown by molecular beam epitaxy. The p‐on‐n planar devices consist of an arsenic‐doped p‐type epilayer (y=0.28) on top of a long wavelength infrared n‐type epilayer (x=0.225, λ=10 μm). The planar junctions were formed by selective pocket diffusion of arsenic deposited by ion implantation. The detailed analysis of the current‐voltage characteristics of these diodes as a function of temperature show that they have high performance and that their dark currents are diffusion limited down to 52 K. The results also show that the R0A values for these devices are highly uniform at 77 K.

HgCdTe double heterostructure injection laser grown by molecular beam epitaxy

While a variety of light‐detecting devices have been made with HgCdTe, little has been done to apply this technology to light‐emitting devices. We report here the successful fabrication and operation of the first HgCdTe injection laser. This stripe‐geometry double‐heterostructure laser was operated under pulsed current at temperatures between 40 and 90 K. At 77 K, the emission wavelength was 2.86 μm with a linewidth of 0.3 meV, and the pulsed threshold current density was 625 A/cm2. The double heterostructure, with a 1.4‐μm‐thick active layer, was grown and in situ doped by molecular beam epitaxy (MBE). The p+ and n+ confinement layers were doped with arsenic and indium, respectively.

Molecular‐beam epitaxy growth and in situ arsenic doping of p‐on‐n HgCdTe heterojunctions

In this paper we present, results on the growth of in situ doped p‐on‐n heterojunctions on HgCdTe epilayers grown on (211)B GaAs substrates by molecular‐beam epitaxy (MBE). Long wavelength infrared (LWIR) photodiodes made with these grown junctions are of high performance. The n‐type MBE HgCdTe/GaAs alloy epilayer in these structures was grown at Ts=185u2009°C and it was doped with indium (high 1014 cm−3 range) atoms. This epilayer was directly followed by the growth, at Ts=165u2009°C, of an arsenic‐doped (1017–1018 cm−3 ) HgTe/CdTe superlattice structure which was necessary to incorporate the arsenic atoms as acceptors. After the structure was grown, a Hg annealing step was needed to interdiffuse the superlattice and obtain the arsenic‐doped p‐type HgCdTe layer above the indium‐doped layer. LWIR mesa diodes made with this material have 77 K R0A values of 5×103, 81, 8.5, and 1.1 Ωu2009cm2 for cutoff wavelengths of 8.0, 10.2, 10.8, and 13.5 μm, respectively; the 77 K quantum efficiency values for these diodes were gre...

Planar p-on-n HgCdTe heterostructure infrared photodiodes on Si substrates by molecular beam epitaxy

We have developed a low temperature procedure for molecular beam epitaxy of CdTe buffer layers on {211} Si wafers and have used Si/ZnTe/CdTe composite substrates for molecular beam epitaxy of double layer Hg1−xCdxTe heterostructures. Planar p-on-n double layer heterostructures were formed by an implantation technique and test diodes were fabricated and characterized. At 77 K, devices with 30×30 μm2 junction area had R0A values in the range 1.5×106–1×107Ωu2009cm2 with a uniform cut-off wavelength of 4.65 μm.

Effect of the dislocation density on minority‐carrier lifetime in molecular beam epitaxial HgCdTe

The photoconductive minority‐carrier lifetime has been measured as a function of temperature and etch‐pit density in n‐type HgCdTe grown by molecular beam epitaxy with a composition range x=0.22–0.23 to determine the limiting recombination mechanisms, particularly those related to dislocation density. In the extrinsic region at temperatures T<77 K, the minority‐carrier lifetime is limited by Shockley–Read recombination. Strong correlation between minority‐carrier lifetime and dislocation density is observed.

HIGH-POWER DIODE-LASER-PUMPED MIDWAVE INFRARED HGCDTE/CDZNTE QUANTUM-WELL LASERS

Diode‐array‐pumped HgCdTe/CdZnTe broad‐stripe quantum‐well lasers operated at 88 K yielded 1.3 W peak power and 10 mW average power per facet at 3.2 μm. The highest operation temperature was 154 K, and the characteristic temperature of the threshold was 16 K. The external quantum efficiency was ∼7.5% at ∼80 K and decreased by an order of magnitude at 150 K.

HgCdTe dual‐band infrared photodiodes grown by molecular beam epitaxy

We report the demonstration of an all molecular beam epitaxy HgCdTe bias‐selectable dual‐band infrared photodetector. The mesa device, an n‐p‐n three layer HgCdTe heterostructure, was in situ doped with arsenic and indium for p‐ and n‐type doping. The device design is similar to a heterostructure floating base transistor. The feasibility of the two‐color bias‐switchable detector was demonstrated by obtaining backside illuminated spectrally pure dual‐band detection at 77 K. Wavelength cutoff (λco) selection to 5.2 μm with 60% quantum efficiency (QE) was obtained by applying a negative bias of −250 meV, and to λco=7.9 μm with 36% QE by applying a positive bias of 250 meV. The current‐voltage characteristics of this device can be described in terms of a simple back‐to‐back diode model.

p‐i‐n HgCdTe photodiodes grown by molecular beam epitaxy

We report the successful molecular beam epitaxy (MBE) growth of in situ arsenic‐ and indium‐doped p‐i‐n HgCdTe double heterostructures. High‐performance, short‐wavelength, infrared (2.09 μm) photodiodes operating at 300 K have been fabricated with these double heterostructures. The observed current‐voltage characteristics and quantum efficiency of these diodes can be explained by assuming that the current components are dominated by generation‐recombination currents. These photodetectors exhibit quantum efficiencies of 78%. Growth of this kind of in situ doped structures indicates that the HgCdTe MBE technology has matured to the point where doped HgCdTe multilayer heterostructures can be grown and used to fabricate advanced infrared electronic devices.

High-power diode-pumped mid-infrared semiconductor lasers

A number of double heterostructure and quantum well lasers with wavelengths approximately 3.1, 3.2, 3.4, 3.85 - 4.1, and 4.5 micrometers have been realized in InAsSb/GaSb and HgCdTe/CdZnTe material systems. Peak powers at the few W level and average power at the few hundred mW-level were obtained from optically pumped broad-area lasers at >= 80 K. Threshold, efficiency, internal loss, and gain saturation studies are reported. A compact laser package was built, using a high-power diode array for pumping and a Stirling pump for cooling. Its performance with a 4-micrometers laser is described.

Molecular beam epitaxy (MBE) HgCdTe flexible growth technology for the manufacturing of infrared photovoltaic detectors

In this paper we present p-on-n heterostructure HgCdTe photovoltaic device data that illustrates the high performance and flexibility in band gap control of the molecular beam epitaxy (MBE) technology. This flexibility demonstration was carried out by growing material for operation in the following cut-off wavelength ((lambda) co) ranges of interest: LWIR [(lambda) co(77 K) equals 9-11 micrometers ], MLWIR [(lambda) co(77 K) equals 6-7 micrometers ], and VLWIR [(lambda) co(40 K) equals 20 micrometers ]. Detailed analyses of the current-voltage characteristics of these diodes as a function of temperature show that their dark currents are diffusion-limited down to 80 K, 50 K, and 30 K for the MLWIR, LWIR, and VLWIR photodiodes, respectively. In general, the RoA device values were uniform for the three band gap ranges when operating under diffusion limited conditions. The planar MBE HgCdTe technology has been further validated with the successful fabrication and operation of 64 X 64 hybrid FPAs.