Selective MOCVD growth of strained (In)GaAs quantum dot active region laser diode on GaAs substrates employing diblock copolymer lithography

Abstract

Semiconductor Laser diodes (LD) employing quantum dot (QD) active region have attracted attention due to the theoretical predictions: low threshold current density and low temperature sensitivity originated from the delta-function-like density of states and small active volume [1]. However, while high performance devices have been demonstrated, the realization of all the predicted advantages has remained challenging. Self-assembled QDs grown by Stranski-Krastanov growth mode suffer from an inhomogeneity in the QD size distribution, as well as an inherent problematic wetting layer [2]. Nanopatterning and selective MOCVD growth offer a more controllable pathway for QD formation, allowing the QD size to be decoupled from the strain state of the material, although the challenges stemming from surface state formation remain a problematic issue [3]. Selectively grown QDs employing nano-patterning prepared by e-beam lithography or atomic force microscopy oxidation can be expensive and time-consuming, depending on the pattern area [4]. Here, we report on the properties of LD employing a dense array of the wetting layer-free, compressively-strained single layer In0.35Ga0.65As QDs as the active region on a nominally singular (001) GaAs substrate (QD Density: 6∼8 × 1010 cm−2), grown by MOCVD.