Donor-related structure observed in the magnetoresistance of high-purity n-GaAs and InP observed under warm electron conditions and at low temperatures

Holmes, S. N.; Wang, P D; Cowan, D.A.; Trager, C.; Stradling, R. A.

doi:10.1088/0268-1242/5/2/004

Cited by 6 publications

(1 citation statement)

References 17 publications

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“…A further complicating factor is that conventional treatments of neutral impurity scattering omit the possibility of inelastic scattering where the impurities are left in an excited state, although such impact excitation of neutral impurities has been detected with InSb [52] and GaAs [53]. Laviolette and Callaway [54] computed the scattering rate from neutral hydrogenic donors in moderately doped semiconductors.…”

Section: Tmentioning

confidence: 99%

Electrical and magneto-optical of MBE InAs on GaAs

Wang

Holmes

et al. 1992

Semicond. Sci. Technol.

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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 -' )

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Section: Tmentioning

confidence: 99%

Electrical and magneto-optical of MBE InAs on GaAs

Wang

Holmes

et al. 1992

Semicond. Sci. Technol.

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Impurity breakdown induced current filaments in n-GaAs

Prettl

Nonlinear Physics of Complex Systems

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FIR photoconductivity at filamentary current flow in n-GaAs in a magnetic field

Голубев

Prettl

1991

Solid State Communications

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A large number of spectral structures are observed by far infrared magneto-photoconductivity in n-GaAs at 4.2K biased above impurity breakdown in a regime where current flow is filamentary. Phase changes are found in the center of the ls-2p+l line and new structures are observed which shift to higher magnetic fields with increasing bias voltage. The large strength and the intensity dependence of the photosignals indicate that the observed phenomena are due to self-organizing effects of the filament. Small variations of the electron population by infrared irradiation may cause substantial rearrangements of the spatial current distribution.At low temperatures the autocatalytic process of impact ionization of shallow impurities in high-purity semiconductors leads to highly nonlinear current-voltage characteristics. At a critical breakdown voltage the impact ionization rate of impurities exceeds the capture rate of free carriers at low concentrations yielding a rapid increase of the current at a practically constant voltage across the sample. At breakdown a strongly ionized channel is formed in the sample constituting a current filament which carries the total current. The increase of the current is then caused by a lateral growth of the current filament.Here we report on peculiarities which were found in the photoconductivity of n-GaAs when the sample was biased in the nonlinear regime of the current-voltage characteristic and subjected to an external magnetic field. Enhancement of resonant structures in magneto-photoconductivity spectra due to free carrier multiplication, resonant negative photoconductivity and even structures which cannot be attributed to optical impurity transitions are observed. The phenomena may qualitatively be understood from the spatial structure of the filamentary current flow in n-GaAs [1] and the Hall voltage which develops across the filament in a magnetic field leading to different free carrier multiplication rates at opposite edges of the filament [2].The measurements were carried out on n-GaAs epitaxial layers prepared on semiinsulating substrates by vapour phase epitaxy. Results are presented for a sample of ND -NA = 2.7 • 1014 cm -s effective donor concentration, NA/ND ----0.35 compensation ratio and 14 #m thickness. The size of the sample was 3 x 5 mm2; ohmic Indium point contacts were alloyed on opposite edges along the shorter side. The sample was immersed 1035 in liquid helium at 4.2 K in the center of a superconducting solenoid. As sketched in the insert of Fig. 2, the epitaxial layer showed the typical nonlinear currentvoltage relation with three characteristic regimes: (1) high-ohmic pre-breakdown current flow, (2) transition regime from high-resistive to low-resistive behaviour and (3) low-ohmic stable post-breakdown regime. The photoconductive response in Faraday configuration was measured for various biasing conditions as a function of the magnetic field strength up to 6 T using a standard load resistor circuit and lock-in technique. As radiation sources an H20 and an HCN...

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Donor-related structure observed in the magnetoresistance of high-purity n-GaAs and InP observed under warm electron conditions and at low temperatures

Cited by 6 publications

References 17 publications

Electrical and magneto-optical of MBE InAs on GaAs

Electrical and magneto-optical of MBE InAs on GaAs

Impurity breakdown induced current filaments in n-GaAs

FIR photoconductivity at filamentary current flow in n-GaAs in a magnetic field

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