High-efficiency infrared light emitting diodes made in liquid phase epitaxy and molecular beam epitaxy HgCdTe layers

Abstract

We report in this article, for the first time the performance of light emitting diodes(LEDs) made in HgCdTe (MCT) epilayers on CdZnTe (CZT) lattice‐matched substrates grown either by liquid phase epitaxy (LPE) or molecular beam epitaxy(MBE).Diodes are n/p homojunctions made by ion implantation. The MCT composition was chosen in order to get the emission wavelength between 3 and 5 μm. Electroluminescence spectra were recorded between 20 K and 300 K. A comparison of the two materials is made, demonstrating that they exhibit similar performances. Internal quantum efficiencies as high as 25% (λ peak=4.1 μm at 77 K) and 6% (λ peak=3.5 μm at 300 K) were obtained on both LPE and MBE materials and they reach a maximum for a temperature of about 90 K. For a material with λ peak=5.5 μ at 77 K, internal quantum efficiency remains as high as 5%. The external quantum efficiency is considerably increased using backside emission through the CZT substrate and optical coupling with a CZT lens: in such conditions 20% of the emitted light could be extracted from the structure. These results show that MCT can already be used for LEDs in the 3–5 μm region.