Local structural models of complex oxygen- and hydroxyl-rich GaP/InP(001) surfaces

Abstract

We perform density-functional theory calculations on model surfaces to investigate the interplay between the morphology, electronic structure, and chemistry of oxygen-and hydroxyl-rich surfaces of InP(001) and GaP(001). Four dominant local oxygen topologies are identified based on the coordination environment: M -O-M and M -O-P bridges for the oxygen-decorated surface; and M -[OH]-M bridges and atop M -OH structures for the hydroxyl-decorated surface (M =In,Ga). Unique signatures in the electronic structure are linked to each of the bond topologies, defining a map to structural models that can be used to aid the interpretation of experimental probes of native oxide morphology. The M -O-M bridge can create a trap for hole carriers upon imposition of strain or chemical modification of the bonding environment of the M atoms, which may contribute to the observed photocorrosion of GaP/InP-based electrodes in photoelectrochemical cells. Our results suggest that a simplified model incorporating the dominant local bond topologies within an oxygen adlayer should reproduce the essential chemistry of complex oxygen-rich InP(001) or GaP(001) surfaces, representing a significant advantage from a modeling standpoint.

Atomic scale analysis of the GaP/Si(100) heterointerface byin situreflection anisotropy spectroscopy andab initiodensity functional theory

“…Regarding solar-hydrogen genera tion for energy storage and renewable-fuel production, tandem structures reach optimum theoretical solar-to-hydrogen effi ciencies applying Si as substrate and 1.6 to 1.8 eV band-gap absorbers [3], The latter could be lattice-matched grown by dilute nitride Ga(N,As)P with theoretical photovoltaic tandem efficiencies close to optimum [4], GaP-related surfaces and their interfaces to water are the subject o f current theoretical [5][6][7] as w ell as experimental [8] studies, and the combination with Si(100) for photoelectrochemical (PEC) diodes is highly desired for water splitting [9], Pseudomorphic GaP/Si(100) serves as a quasisubstrate for the subsequent industrially scal able growth o f high-performance electronic and optoelectronic devices, such as multijunction solar cells [4,10] …”

The interface of GaP(100) and H2O studied by photoemission and reflection anisotropy spectroscopy

“…semiconductors InP and GaP has been subject of several theoretical investigations [11][12][13], but experimental data only exists for InP(110) [14,15] and not for GaP to our knowledge.…”

Water-induced modifications of GaP(100) and InP(100) surfaces studied by photoelectron spectroscopy and reflection anisotropy spectroscopy

“…13,25 Oxygen exposure leads to a strong feature between 6 and 8 eV below E F . Compared to calculations of Wood et al, 10 this would point towards Ga-O-P as a structural motif, which is expected to exhibit the highest density of states in the energy range of the considered structures. The peak around 2.5 eV in Fig.…”

“…Several theoretical studies investigated this question for GaP(100) and InP(100) identifying surface motifs which can act as charge carrier traps. [9][10][11] Water adsorption studies in ultra-high vacuum (UHV) on cleaved InP(110) samples revealed the Figure 1. Ball-and-stick model of the III-rich, mixed dimer and the P-rich, hydrogen stabilized surface reconstructions, which are typical for MOVPE-prepared InP(100) and GaP(100).…”