Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy

Abstract

A route towards optimisation of uniformity and density of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V/III ratio, a fact which was shown to be valid when either AsH 3 (arsine) or tertiary-butyl-arsine (TBA) were used as group V precursors. Once the optimum V/III ratio was found, the size distribution was further improved by adjusting the nominal thickness of deposited InAs material, resulting in an optimum thickness of 1.8 monolayers of InAs in our case. The number of coalesced dots was minimised by adjusting the growth interruption time to approximately 30 s. Further, the uniformity was improved by increasing the growth temperature from 485 °C to 520 °C. By combining these optimised parameters, i.e. a growth temperature of 520 °C, 1.8 monolayers InAs thickness, 30 s growth stop time and TBA as group V precursor, a full-width-half-maximum (FWHM) of the low temperature luminescence band of 40 meV was achieved, indicating a narrow dot size distribution.

Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors

“…Details about the growth conditions have been described in earlier publications. 9,10 From atomic force micrographs, the QD density and the average QD diameter and height have been estimated to be 9 ϫ 10 10 cm −2 , 16 nm, and 3.5 nm, respectively. The vertical DWELL IP structure was fabricated by standard optical lithography, etching, and metallization techniques.…”

InAs quantum dot growth on AlxGa1−xAs by metalorganic vapor phase epitaxy for intermediate band solar cells

“…A maximum density is reached for a TMIn flow of 175 sccm (1 ML/s), which corresponds to a relatively low V/III ratio of 6.4. Further reduction of the V/III ratio increases the In adatom mobility on the surface due to the low density of As atoms, 24,25 decreasing the QDs density and increasing their size. Best conditions for QD-IBSCs were found to be for QD growth at 490 C and at a rate of 1 ML/s, resulting in a QD density of 1.7 Â 10 10 /cm 2 and a homogeneity of 49%.…”

Capping of InAs/GaAs Quantum Dots for GaAs Based Lasers

“…The V/III ratio for InAs growth was 0.5, 1 and 2 for samples A1, A2 and A3. Such a low V/III ratio was used to improve quantum dot size homogeneity (Hoglund et al, 2006). However, very low V/III ratio during InAs growth and at the beginning of capping layer growth enabled us to achieve In rich (4×2) surface reconstruction.…”