The fundamental band gap in bulk CdxHg1-xTe is direct for all x-values, and can be compositionally tuned from -0.14eV in the semi-metal HgTe (x = 0) to 1.49eV in CdTe (x = 1) at 300K. Over the same range of x-values, the lattice parameter differs by only 0.3%, which allows a great variety of heterostructures, including quantum well structures, to be made without considering strain effects. In quantum well structures, the energies of the discretely quantized bound energy levels are determined by both the composition in the well and barrier layers and the thickness of the well layer. The emission wavelength of a CdxHg1-xTe quantum well light emitting device can hence be tuned both by varying x and also by varying the well thickness, in contrast to a bulk device where the emission wavelength can be tuned only by compositional changes.
We will present temperature- and laser intensity dependent photoluminescence measurements of a CdxHg1-xTe multiple quantum well (MQW) structure grown by molecular beam epitaxy (MBE). The experimental data are compared to calculated values for the transition energies. The photoluminescence spectra were recorded by means of a Fourier transform infrared (FT-IR) spectrometer.
The MQW structure consists of four x = 0.35 quantum wells of width 10nm surrounded by x = 0.60 barrier layers. To be able to measure the x-value of the quantum wells by means of transmission spectroscopy, the MQW structure was grown on top of a 4µm buffer layer of the same composition as the quantum well layers.
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