Highly Strained III-V-V Coaxial Nanowire Quantum Wells with Strong Carrier Confinement.

Yunyan Zhang,H Aruni Fonseka,David J Mowbray,Anton Velichko,George Davis,Dhruv Saxena,Patrick W Parkinson,Anders Gustafsson,Suguo Huo,Ana M Sanchez,James A Gott,Huiyun Liu,Tillmann Godde,Martin Aagesen

doi:10.1021/acsnano.9b01775

Abstract

Coaxial quantum wells (QWs) are ideal candidates for nanowire (NW) lasers, providing strong carrier confinement and allowing close matching of the cavity mode and gain medium. We report a detailed structural and optical study and the observation of lasing for a mixed group-V GaAsP NW with GaAs QWs. This system offers a number of potential advantages in comparison to previously studied common group-V structures (e.g., AlGaAs/GaAs) including highly strained binary GaAs QWs, the absence of a lower band gap core region, and deep carrier potential wells. Despite the large lattice mismatch (∼1.7%), it is possible to grow defect-free GaAs coaxial QWs with high optical quality. The large band gap difference results in strong carrier confinement, and the ability to apply a high degree of compressive strain to the GaAs QWs is also expected to be beneficial for laser performance. For a non-fully optimized structure containing three QWs, we achieve low-temperature lasing with a low external (internal) threshold of 20 (0.9) μJ/cm2/pulse. In addition, a very narrow lasing line width of ∼0.15 nm is observed. These results extend the NW laser structure to coaxial III–V–V QWs, which are highly suitable as the platform for NW emitters.

Highlights

Semiconductor nanowires (NW) lasers provide strong optical mode confinement in a very small volume, allowing laser diameters on the order of a few hundred
Threshold reduction can be achieved by confining carriers within a nanostructure to benefit from the enhanced gain and improved temperature stability;[18,19] both quantum dots (QDs)[15] and coaxial quantum wells (QWs)[20] have been used as the gain medium
Scanning transmission electron microscope (STEM) images show that the first third of the NW length has a pure zinc-blende (ZB) structure without stacking faults, the middle third is lightly twinned, and the final third, toward the tip, is more defective (Figure 1a, Supporting Information S2)

Summary

Introduction

Semiconductor nanowires (NW) lasers provide strong optical mode confinement in a very small volume, allowing laser diameters on the order of a few hundred. While optically pumped NW lasers have been demonstrated,[7,12−15] further reducing the threshold is critical for many applications as well as realizing electrically injected devices.[16,17] Threshold reduction can be achieved by confining carriers within a nanostructure to benefit from the enhanced gain and improved temperature stability;[18,19] both quantum dots (QDs)[15] and coaxial quantum wells (QWs)[20] have been used as the gain medium. There have been relatively few demonstrations of the use of coaxial QWs to reduce the threshold of NW lasers,[21−23] with all reports using III−III−V, common group-V material systems (e.g., AlGaAs/GaAs),[24−30] which have some disadvantages associated with the challenges of growing III−III−V core. There are large differences in the optimal growth conditions for each species, especially in the growth temperature.[32,33] This makes the growth of III−III−V NWs difficult, especially for the self-catalyzed growth mode.[32,34] As a result, III−III−V NWs with QWs are commonly built on binary core

Methods

Results

Conclusion