Resonant cavity light emitting diodes for the 3–5 μm range

Abstract

We have realized in the mid-infrared range, resonant cavity light emitting diodes (RCLEDs). The devices, grown by molecular beam epitaxy of CdHgTe alloys, consist of a bottom Bragg reflector, a half wavelength cavity, n-doped at the beginning (10 18 cm −3) and p-doped at the end (10 18 cm −3), containing an active layer at the antinode position, and a top gold mirror which is also used as an ohmic contact. We measure a room temperature electroluminescent spectrum full width at half maximum (FWHM) of 9 meV, which is much less than the inhomogeneous linewidth of CdHgTe quantum wells (QWs). Measurements performed at different temperatures (between 25 and 250 K) show that the temperature could be an efficient means for tuning or detuning the device. Furthermore, we obtained, at low temperature, an efficient transfer to the cavity mode due to the good overlap of the Bragg reflector bandwidth with the CdHgTe emitting spectrum. We have thus demonstrated for the first time the feasibility of infrared RCLEDs working up to room temperature. We have also shown that even a relatively low quality factor microcavity can greatly improve the spectral and spatial characteristics of infrared emitters in the 3–5 μm range.