Electrical and magneto-optical of MBE InAs on GaAs

Abstract

The electrical quality of lnAs films grown on GaAs substrates by MBE is found to be optimum for growth temperatures close to 490 "C. The Hall mobility for such samples is80000cm2V-'s-' at 77 K for film thicknesses of 5 pm but falls to about 10 000 cm2 V -' s -' at a thickness of 0.05 pm. The carrier concentration in the bulk of the films is believed to be less than 10'5cm-3. The carrier concentration rises and the mobility falls as the growth temperature is varied on either side of this optimum value, reaching 2.5 x 10'8cm-3 and 15000cm2V-'s-' at 77 K respectively for a growth temperature of 350 "C.Extremely sharp free-carrier cyclotron resonance and shallow donor lines are observed from the bulk of the film in far-infrared magneto-optical measurements, together with a very broad but strong cyclotron resonance line from an electron accumulation layer believed to be at the surface. The width of the cyclotron resonance line is consistent with a bulk mobility of the order of 200000cm2V-' 5 -' and the decrease in Hall mobility, together with the apparent increase in carrier concentration with decreasing film thickness, can be explained by the parallel conductance from the two-dimensional electron gas at the surface. There is no evidence for a significant reduction in mobility from the high density of threading dislocations caused by the mismatch with the GaAs substrate. The sharpness of the cyclotron resonance allows an accurate value for the band edge effective mass to be determined of 0.0236 f 0.0003m. with a pressure coefficient of ' +2.0% kbar-'. The donor lines are sufficiently sharp that central cell structure due to two different donor contaminants can be detected, and these donors are thought to be sulphur and selenium originating from the As source material. Certain of the transitions detected are too energetic to be from the shallow donors and these are thought to arise from singly ionized double donors which may be arsenic antisites.Silicon is found to act as a donor dopant up to high concentrations (6 x 10'ecm-3 where the mobility is 2000 cm2 V -' s -' )

FIR Magnetooptical Measurements on MOCVD Grown InAs

“…In the spectra one can see two pronounced, narrow peaks. Additionally, as was the case with MBE samples [1], for the MOCVD samples a broad structure on transmission and photoconductivity spectra is also present. It is clear that the broad structure, together with the two narrow peaks, is shifting towards higher magnetic fields with increasing energy of the FIR photons.…”

“…Although in general there is little known about shallow donors in that material, there are groups of researchers who did observe intra-shallow-donor transitions in MBE-grown thin InAs layers on GaAs (see, e.g., Ref. [1] and references therein), as well as cyclotron resonance (CR). However the observed spectra [1] show surprisingly narrow lines of CR, which cannot be compared with the observed values of the carrier mobility obtained from Hall and conductivity measurements in the same samples.…”

“…[1] and references therein), as well as cyclotron resonance (CR). However the observed spectra [1] show surprisingly narrow lines of CR, which cannot be compared with the observed values of the carrier mobility obtained from Hall and conductivity measurements in the same samples. The authors of Ref.…”

“…The authors of Ref. [1] believe that the extremely narrow lines found in the spectra originate from cyclotron resonance and impurity shifted cyclotron resonance. Unambiguous interpretation of the half-widths of these lines is, however, still under discussion.…”

High accuracy magnetic field sensors with wide operation temperature range

“…Direct overgrowth of InAs causes propagation of the dislocations from nucleation layer to the overlying heterostructure active layers, enhancing the scattering of electrons, thus increasing the device resistivity. In the direct epitaxial growth of the relaxed InAs films, the dislocations' density decreases quickly with an increase of film thickness, and the quality improvement is observed with a layer thickness of > 1.5 ÷ 4 microns [5,6]. At the standard speeds and temperatures above 500 °C, the growth of InAs on GaAs leads to the formation of a rough surface and stacking faults.…”