Effects of substrate miscut on the properties of InGaP solar cells grown on GaAs(001) by solid-source molecular beam epitaxy

Abstract

The growth of ternary InGaP alloys is often susceptible to atomic ordering, which leads to an anomalous bandgap reduction as well as the formation of antiphase boundaries (APBs). The effect of substrate miscut on the performance of lattice-matched In0.52Ga0.48P solar cells grown on GaAs(001) substrates by solid-source molecular beam epitaxy (SS-MBE) is investigated. A B-type miscut enhanced single-variant atomic ordering even with SS-MBE, resulting in a bandgap (Eg) reduction from 1.87 eV for an alloy grown on an exact substrate to 1.85 eV for that grown on the substrate miscut 6° toward (111)B. Conversely, an A-type miscut suppressed the formation of atomic ordering, resulting in the Eg widening of the alloy grown on the substrate miscut 6° toward (111)A to 1.89 eV. With regard to solar cell performance, InGaP solar cells grown on A-type miscut substrates enhanced the open-circuit voltage (VOC) and WOC (= Eg/q − VOC) because of the low degree of atomic ordering. Large improvements in WOC and efficiency to 0.58 V and 10.93%, respectively, were obtained for the cell grown on the substrate miscut 2° toward (111)B. A reduction in the number of APBs due to single-variant atomic ordering was related to this latter result.

Enhancement of open-circuit voltage in InGaP solar cells grown by solid source molecular beam epitaxy

“…The above-mentioned PL results can be explained by the atomic ordering in these materials. Figure 3 shows TED patterns measured for selected areas of InGaP layers grown on miscut substrates at (a) 480 °C and 1.0 µm=h 18) and (b) 510 °C and 1.5 µm=h. Large spots represent fundamental reflections, while small spots and streaks indicate superlattice reflections.…”

“…Lattice-matched InGaP single-junction SCs and InGaP=GaAs DJSCs were fabricated on p + -GaAs(100) substrates miscut 2°t owards (111)B (denoted as miscut) using a Riber compact 21 solid-source MBE system equipped with valved cracking cells to achieve stable phosphorous and arsenic fluxes. 18,21) The detailed cell structure is shown in Fig. 1.…”

“…16,17) On the other hand, we have recently reported atomic ordering that was formed in InGaP alloys grown by solid-source molecular beam epitaxy (SS-MBE), and the use of substrate miscutting helped in controlling the atomic ordering formation in InGaP, resulting in an improved V OC . 18) However, detailed studies on the effects of growth conditions on atomic ordering in InGaP alloys grown by SS-MBE are scarce, because there have been few studies on the growth of thick InGaP films by SS-MBE. 19,20) In this work, we study the effects of growth rate and growth temperature on the properties of atomic ordering as well as the performance of InGaP cells.…”

Fabrication of GaAs solar cells grown with InGaP layers by hydride vapor-phase epitaxy

“…After the HVPE growth process, a front AuGeNi=Au finger was formed, and a mesa isolation was performed using a standard photolithography system and electron beam evaporator. 22) The metallization was performed at 350 °C for 2 min under a nitrogen ambient. Ti=Au was used as the back electrode.…”

Growth of InGaAs Solar Cells on InP(001) Miscut Substrates Using Solid‐Source Molecular Beam Epitaxy

“…Herein, we investigate the effect of the surface diffusion of adatoms on the structural and optical properties of InGaAs solar cells, in terms of T g and the surface miscut. Miscut substrates can promote steps in a particular direction, leading to direct control of the adatoms' surface diffusion . Thus far, the effect of miscut substrates on the InGaAs solar‐cell performance have not been investigated.…”