CdxHg1−xTe is a II-IV semiconductor with a variable direct band gap
ranging from -0.14 eV in HgTe (x = 0) to 1.5 eV in CdTe (x = 1) at room temperature. The tunable band gap makes it useful in detectors and emitters of light in both the 3-5 µm and the 8-12 µm window in the atmosphere, where the absorption of light is low. Over the entire compositional range, the lattice constant changes by only 0.3 %, which allows a great variety of heterostructures, including quantum wells, to be made.
We will present the temperature dependence of the photoluminescence from a 4 µm Cd0.35Hg0.65Te layer compared to a Cd0.35Hg0.65Te/ Cd0.6Hg0.4Te multiple quantum well (MQW) structure. To ensure that the quality and composition of the bulk and quantum well layers were as similar as possible, the MQW structure was grown on top of the bulk layer (4 µm) in the same growth run. The sample was grown by molecular beam epitaxy (MBE).
The photoluminescence spectra were recorded by means of a Fourier transform infrared (FTIR) spectrometer at temperatures ranging from 10 K to 300 K. Due to Auger recombination, the bulk peak intensity decreases much faster with temperature than the MQW peak. The bulk peak decreases to a minimum around 100 K, and then increases with increasing temperature up to room temperature, in contrast to the MQW peak, which decreases gradually up to room temperature.
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