I. Madni

Recent progress in MBE grown HgCdTe materials and devices at UWA

HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching. In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia (UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn structures.

Controlled vapour-phase deposition synthesis and growth mechanism of Bi2Te3 nanostructures

This work presents a study on the controlled growth and the growth mechanism of vapour-phase deposited two-dimensional Bi2Te3 nanostructures by investigating the influence of growth conditions on the morphology of Bi2Te3 nanostructures. The formation of a hexagonal plate geometry for Bi2Te3 nanostructures is a consequence of the large difference in growth rate between crystal facets along 〈0001〉 and 〈11 2¯0〉 directions. Under low Ar carrier gas flow rates (60–100 sccm), the growth of Bi2Te3 nanoplates occurs in the mass-transport limited regime, whereas under high carrier gas flow rates (130 sccm), the growth of Bi2Te3 nanoplates is in the surface-reaction limited regime. This leads to an increase in the lateral size of Bi2Te3 nanoplates with increasing the Ar carrier gas flow rate from 60 to 100 sccm, and a decrease in size for a flow rate of 130 sccm. In addition, the lateral size of Bi2Te3 nanoplates was found to increase with increasing growth time due to the kinetic characteristics of material growth...

Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg1−xCdxTe (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 1016 cm−3 to 6 × 1017 cm−3 without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 104 cm2/V s to 7 × 103 cm2/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 1016 cm−3 to 6 × 1017 cm−3. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 ...

Correction to: Investigation of MBE-Growth of Mid-Wave Infrared Hg 1− x Cd x Se

In the original article, G. A. Umana-Membreno’s name is incorrect. It is corrected as reflected here.

Structural and electrical properties of Iodine doped Hg 1−x Cd x Te films grown by MBE

Iodine (I) doping in mercury cadmium telluride (Hg_1-xCd_xTe) grown by molecular beam epitaxy (MBE) on CdZnTe substrates with cadmium-iodide (CdI₂) as the dopant source was investigated. I doping concentration in the samples was controlled by CdI₂ source temperature that varied in 110°C-150°C range. Depending upon I doping concentration, the electrical conductivity at 77K for as grown films varied in the 3×10³ Ω^-1m^-1 - 6×10⁴ Ω^-1 m^-1 range and was about of six to ten orders of magnitude higher than those of non-doped HgCdTe films. The Hall coefficient showed classical n-type extrinsic behavior. The electron mobility for lower doping level was observed to be as high as that in an indium-doped material reported in literature [1]. The x-ray diffraction (XRD) studies revealed that there was no prominent change in crystal structure with increasing doping concentration. However, atomic force microscopy (AFM) measurements showed that dislocation densities and consequently defect concentration and size increased with increasing doping concentration.