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Title: The pressure dependence of the effective masses in gallium arsenide and related compounds
Author: Tatham, Harry L.
ISNI:       0000 0001 3499 5956
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1982
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High pressure has been used to study electrical transport properties of GaAs, InSb and In[1-x]Ga[x]As[y]P[1-y], grown lattice matched to InP. The pressure dependence of the r[c1] effective mass has been determined in InSb at ~ 160 K to ~ 14 kbar and in GaAs at ~ 300 K to ~ 22 kbar, using measurements of the magnetophonon effect in the transverse magnetoresistance. The pressure coefficients obtained are: InSb (160 K): dm*/dP = 6.2 + 0.2 % kbar[-1] GaAs (300 K): dm*/dP = 0.63 + 0.05 % kbar[-1] Good agreement is acquired between the observed m* variation in InSb and simple three band k. p. theory. For GaAs reasonable agreement is obtained using the simpler k. p theory but the agreement becomes worse as a more refined theory is considered which takes account of higher lying minima. The electron mobility in high purity InSb has been studied at room temperature as a function of hydrostatic pressure to 15 kbar. The mobility, which reduced by ~ 50% to 15 kbar, is shown to be dominantly controlled by polar optical scattering and electron scattering by holes. The direct energy gap pressure coefficient for InSb is measured to be: dEo/dP = (14.6 + 0.2) x 10[-3] eV kbar -1 The electron and hole mobilities in n-and p-type samples of the quaternary alloy In1-xGaxAsyP1-y, grown lattice-matched to, semi-insulating Fe doped (100) InP substrates have been studied as a function of hydrostatic pressure to 16 kbar, at room temperature. The electron mobility reduced by ~ 20% to 15 kbar for samples with y = 0.5, while the hole mobility reduced by approximately a fifth of the electron mobility values to 15 kbar. These results confirmed the presence of alloy scattering. The temperature dependence of the Gunn threshold in GaAs has been investigated, with Monte Carlo calculations giving reasonable agreement to experimental results. The temperature coefficient obtained is 1/Ip (300 K) dl p/dT = - 2. 4 x 10[-3] K[-1] which is independent of carrier concentration, and 1/Vp(300 K) dVp/ dT is positive and decreases with increasing carrier concentration. The results support a r-L-X ordering of the band structure of GaAs at atmospheric pressure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physics, general