Yellow-green strained-InGaP quantum-well epitaxial-transparent-substrate light emitting diodes

Abstract

We present a strained-InGaP quantum-well light emitting diode (LED) operating in the green to yellow region of the visible spectrum. The active layer consists of an undoped, compressively strained In0.32Ga0.68P or In0.37Ga0.63P quantum well deposited via metalorganic chemical vapor deposition on a transparent In0.22(Al0.2Ga0.8)0.78P/∇x[Inx(Al0.2Ga0.8)1−xP]/GaP virtual substrate. Epitaxial-transparent-substrate LEDs based on this structure emit with a primary peak at 590 nm and a secondary peak at 560 nm. The highest LED power of 0.18 μW per facet at 20 mA was observed for a quantum well composition of In0.32Ga0.68P and a threading dislocation density on the order of 7×106 cm−2. The same device structure intentionally grown with a threading dislocation density on the order of 5×107 cm−2 exhibited an identical spectral shape with a reduced power of 0.08 μW per facet at 20 mA. Based upon superspots present in transmission electron diffraction from the quantum well region, the observed spectrum is the result of emission from ordered and disordered domains in the active region. Devices with a quantum well composition of In0.37Ga0.63P and an overall threading dislocation density on the order of 5×107 cm−2 emit at a single peak wavelength of 588 nm with a power of 0.06 μW per facet at 20 mA.