Valence-band offsets of CoTiSb/In0.53Ga0.47As and CoTiSb/In0.52Al0.48As heterojunctions

Abstract

The valence-band offsets, ΔEv, between semiconducting half-Heusler compound CoTiSb and lattice-matched III-V In0.53Ga0.47As and In0.52Al0.48As heterojunction interfaces have been measured using X-ray photoemission spectroscopy (XPS). These interfaces were formed using molecular beam epitaxy and transferred in situ for XPS measurements. Valence-band offsets of 0.30 eV and 0.58 eV were measured for CoTiSb/In0.53Ga0.47As and CoTiSb/In0.52Al0.48As, respectively. By combining these measurements with previously reported XPS ΔEv (In0.53Ga0.47As/In0.52Al0.48As) data, the results suggest that band offset transitivity is satisfied. In addition, the film growth order of the interface between CoTiSb and In0.53Ga0.47As is explored and does not seem to affect the band offsets. Finally, the band alignments of CoTiSb with GaAs, AlAs, and InAs are calculated using the density function theory with the HSE06 hybrid functional and applied to predict the band alignment of CoTiSb with In0.53Ga0.47As and In0.52Al0.48As. Good agreement is found between the calculated valence-band offsets and those determined from XPS.

Growth, electrical, structural, and magnetic properties of half-Heusler CoTi1−xFexSb

“…3(b). For the CoTiSb spectrum, good agreement is observed with the DOS and resembles previously reported spectra at similar excitation energies 16,18,32,35 . For the x=0.2 and x=0.5 films, the spectra show similar structure to that of CoTiSb with only a few small binding energy shifts, consistent with our calculated DOS.…”

“…During growth, a (2x1) surface reconstruction was inferred from bright, streaky RHEED patterns for x≤0.5 (Fig 1), similar to that observed in intrinsic CoTiSb 15,32 . For the pure CoFeSb film, the RHEED pattern consisted of faint streaks as well as bulk diffraction spots indicating roughening of the surface and lower film quality.…”

Formation of two-dimensional electron and hole gases at the interface of half-Heusler semiconductors

“…Only recently the existence of a 2DHG has been demonstrated in the case of SrTiO 3 /LaAlO 3 due to the difficulty in controlling the formation of defects that act to compensate holes [23]. Since, in HH compounds, the valence bands are not too low, and the conduction bands are not too high in an absolute energy scale, i.e., they are comparable to III-V semiconductors [17], we expect that compensation will not be a difficult problem to achieving both 2DEGs and 2DHGs in HH interfaces, as long as sharp interfaces are fabricated.…”

“…They have attracted wide interest due to their potential application in spintronics [14], solar cells [15], and thermoelectrics [16]. Many HH are lattice matched to and can be epitaxially grown on III-V semiconductor substrates [17], adding great flexibility in device design and integration with conventional semiconductors. Here, we show that interfaces of HH semiconductors exhibit two-dimensional electron or hole gases (2DEG or 2DHG), without any chemical doping.…”

Fermi-Level Pinning in ErAs Nanoparticles Embedded in III–V Semiconductors

“…We note that the results in Figure e–g display an interesting trend. If the known band offsets between the III–V semiconductors AlAs, GaAs, and InAs are taken into account, , the Fermi level in the nanocomposite material, i.e., with 1.71 nm nanoparticles in the different III–V semiconductors, is pinned at the same energy with respect to the vacuum level, as shown in Figure . This result can also be extended to alloys of these three semiconductor materials, as is also included in Figure .…”