Growth of self-assembled InP quantum islands for red-light-emittinginjection lasers

摘要

In order to achieve laser emission in the visible part of thenspectrum, we have investigated the growth of self-assembled InP quantumndots on GaInP by low-pressure metal-organic vapor phase epitaxy (MOVPE)nusing the Stranski-Krastanow growth mode. Unlike the well-establishednInAs-GaAs system, when InP is deposited on GaInP, typically, two typesnof coherently strained islands with different sizes are formed. A highndensity of small islands is favored when using growth conditions with anreduced surface diffusion, i.e., low temperatures, high growth rates,nand substrates with high misorientation angles. After the deposition ofn3.4 monolayers of InP at 580°C on GaAs-substrates with a surfacenangle of 15° to the next (111)B-plane, 2.1010 InP dotsnper square centimeter with an average height of 4 nm were assembled. Thenemission of these InP islands at 1.72 eV (4.2 K) shows an inhomogeneousnbroadening of 42 meV because of the size fluctuation of the quantumndots. At 90 K, lasing from self-assembled InP quantum islands wasnobserved above a threshold current density of 288 A/cm2. Thendetected laser line is located at 1.8 eV, about 80 meV higher than isnthe ground-state transition energy. We attribute this behavior to lasingnfrom excited states in agreement with power-dependent photoluminescencenexperiments. For temperatures above 150 K, the threshold current densitynincreases dramatically because of a thermally activated escape ofncarriers up to 4.9 k17/cm2 at room temperature, where thencharacteristic temperature is 35 K. Injection lasers containing stackednInP quantum islands and AlGaInP barrier layers with a higher band offsetnmay exhibit an improved temperature dependence