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GaSb grown on GaAs through interfacial misfit (IMF) arrays grown via molecular beam epitaxy has been heavily studied; there is limited research, however, on IMF growth through metal-organic vapor phase epitaxy. To demonstrate viability for integration in a multijunction solar cell for terrestrial use, it is imperative to demonstrate high quality GaSb grown on GaAs through metal-organic vapor phase epitaxy. The preferred gallium precursors for n-type and p-type GaSb for longest minority carrier diffusion length were determined to be trimethylgallium and triethylgallium, respectively. A heteroepitaxial GaSb-on-GaAs device attained an open-circuit voltage of 190 mV and an efficiency of 2.2%. Extracted threading dislocation density from the minority carrier lifetime for the heteroepitaxial GaSb-on-GaAs device was determined to be 7.5 × 10 6 cm − 2 . In a modeled multijunction solar cell, this device attributes to an overall efficiency of 33.1% under AM1.5g illumination. [ABSTRACT FROM AUTHOR]

Heterogeneous self-assembly of III–V nanostructures on inert two-dimensional monolayer materials enables novel hybrid nanosystems with unique properties that can be exploited for low-cost and low-weight flexible optoelectronic and nanoelectronic device applications. Here, the pseudo-van der Waals epitaxy (vdWE) growth parameter space for heterogeneous integration of InAs nanowires (NWs) with continuous films of single layer graphene (SLG) via metalorganic chemical vapor deposition (MOCVD) is investigated. The length, diameter, and number density of NWs, as well as areal coverage of parasitic islands, are quantified as functions of key growth variables including growth temperature, V/III ratio, and total flow rate of metalorganic and hydride precursors. A compromise between self-assembly of high aspect ratio NWs comprising high number density arrays and simultaneous minimization of parasitic growth coverage is reached under a selected set of optimal growth conditions. Exploration of NW crystal structures formed under various growth conditions reveals that a characteristic polytypic and disordered lattice is invariant within the explored parameter space. A growth evolution study reveals a gradual reduction in both axial and radial growth rates within the explored timeframe for the optimal growth conditions, which is attributed to a supply-limited competitive growth regime. Two strategies are introduced for further growth optimization. Firstly, it is shown that the absence of a pre-growth in situ arsine surface treatment results in a reduction of parasitic island coverage by factor of ∼0.62, while NW aspect ratio and number densities are simultaneously enhanced. Secondly, the use of a two-step flow-modulated growth procedure allows for realization of dense fields of high aspect ratio InAs NWs. As a result of the applied studies and optimization of the growth parameter space, the highest reported axial growth rate of 840 nm min−1 and NW number density of ∼8.3 × 108 cm−2 for vdWE of high aspect ratio (＞80) InAs NW arrays on graphitic surfaces are achieved. This work is intended to serve as a guide for vdWE of self-assembled III–V semiconductor NWs such as In-based ternary and quaternary alloys on functional two-dimensional monolayer materials, toward device applications in flexible optoelectronics and tandem-junction photovoltaics. [ABSTRACT FROM AUTHOR]

Abstract: During quantum dot (QD) growth, substrate misorientation has been shown to play a role in the QD growth mechanism, changing their size, shape and density. Since various misorientation angles are used in production of solar cells, this work investigates QD enhanced GaAs p-i-n solar cells grown using the Stranski–Krastanov (SK) growth method on substrates misoriented either 2° or 6° off the (100) in the direction. Results of this work show that 2° misoriented samples have a lower critical thickness for InAs QD formation as compared to the 6° misorientation: ∼1.7 monolayers (ML) versus∼1.8ML, respectively. In addition, the 6° substrates showed a more uniform QD density and size distribution of QDs without significant QD coalescence. Photoluminescence of both substrate types shows that the QD ground state transitions are similar in wavelength. Results of the solar cells under one sun illumination show that QD cells grown on both 2° and 6° substrates have higher short-circuit current density than comparable cells without QD and maintain a high open-circuit voltage. The QD contributed short-circuit current density was normalized for QD size and density for both the 2° and 6° samples. Values of 360A/cm2 per cm3 of InAs and 400A/cm2 per cm3 of InAs were found for the 2° and 6° samples, respectively. For both substrate types, the reduced number of coalesced QDs promoted effective strain balancing, while the increased QD density lead to strong QD absorption. [Copyright &y& Elsevier]