Punctuated growth of InAs quantum dashes-in-a-well for enhanced 2-μm emission

Abstract

InAs quantum dashes (Qdash) engineered to emit near 2 μm are envisioned to be promising quantum emitters for next-generation technologies in sensing and communications. In this study, we explore the effect of punctuated growth (PG) on the structure and optical properties of InP-based InAs Qdashes emitting near the 2-μm wavelength. Morphological analysis revealed that PG led to an improvement in in-plane size uniformity and increases in average height and height distribution. A 2 × boost in photoluminescence intensity was observed, which we attribute to improved lateral dimensions and structural stabilization. PG encouraged formation of taller Qdashes while photoluminescence measurements revealed a blue-shift in the peak wavelength. We proposed that the blue-shift originates from the thinner quantum well cap and decreased distance between the Qdash and InAlGaAs barrier. This study on the punctuated growth of large InAs Qdashes is a step toward realizing bright, tunable, and broadband sources for 2-μm communications, spectroscopy, and sensing.

Fig. 1

a Schematic structure of the InAs quantum dashes. b Punctuated growth scheme of the InAs quantum dash active region

Fig. 2

a Reflection high-energy electron diffraction (RHEED) images obtained along the $\left[110\right]$ and $\left[1,\overline{1},0\right]$ at different instances of the quantum dash growth. b Time series of a single row (marked with the white line) in the RHEED images along $\left[1,\overline{1},0\right]$ during the growth of the PG-2 sample

Fig. 3

a Atomic force microscope (AFM) images of the surface quantum dashes capped by InAlGaAs. b Representative line profiles along $\left[1,\overline{1},0\right]$ direction obtained from the AFM scans. c Distribution of quantum dash heights. d Distribution of quantum dash lengths. e Summary of average height (top), length (middle), and linear quantum dash density (bottom)

Fig. 4

a Room temperature photoluminescence spectra of the quantum dashes grown with different punctuation strategies and their corresponding b λ-integrated intensity, c peak wavelength and d full-width at half maximum values

Fig. 5

a, b Scanning transmission electron microscope images, schematic illustration and band alignment of the a CG and b PG-3 quantum dashes. c Bright-field TEM image of the PG-3 sample under (002) two-beam condition and corresponding selected area electron diffraction image. Qdashes are labeled with the red arrows

Fig. 6

a Low temperature photoluminescence spectra for the PG-3 quantum dashes. b–d Temperature-dependence of the b peak wavelength, c full-width at half-maximum value, and d integrated intensity plotted against 1000/T with the fitted curve. e–h Activation energy trends and schematic diagrams illustrating the origin of the trends