Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

We report on green (550-560 nm) electroluminescence (EL) from (Al<inf>0.5</inf>Ga<inf>0.5</inf>)<inf>0.5</inf>In<inf>0.5</inf>P-(Al<inf>0.8</inf>Ga<inf>0.2</inf>)<inf>0.5</inf>In<inf>0.5</inf>P double p-i-n heterostructures with monolayer-scale tensile strained GaP insertions in the cladding layers and light-emitting diodes (LEDs) based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. Cross-sectional transmission electron microscopy studies indicate that GaP insertions are flat, thus the GaP-barrier substrate orientation-dependent heights should match the predictions of the flat model. At moderate current densities (∼500 A/cm²) the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (∼550 nm at room temperature). At high current densities (>1 kA/cm²) a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4 kA/cm², whereas no saturation is revealed for (211)-grown structures up to the current densities above 14 kA/cm². We attribute the effect to the surface orientation-dependent engineering of the GaP band structure which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p- doped (Al<inf>0.8</inf>Ga<inf>0.2</inf>)<inf>0.5</inf>In<inf>0.5</inf>P cladding layers.