Pressure Dependence of the Electron Effective Mass in GaAs up to the 1s(Γ)‐1s(X) Crossover

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The effect of hydrostatic pressure (P) on the k = 0 conduction band mass m (P) in lightly Si‐doped GaAs is studied by far‐infrared magnetospectroscopy. The electron cyclotron resonance (CR) at (T = 17 K), and the 1s‐2p+ absorption of Si donors (at T = 4.2 K), are measured up to 40 kbar under fields of 6 to 9 T by Fourier transform and laser magnetotransmission techniques. DX‐center trapping is avoided by visible illumination. A double‐bellows diamond‐anvil cell and 36 mm bore magnet enable in situ P‐B‐T tuning. The slopes dE/dB for the CR and 1s‐2p+ peaks decrease with pressure in accordance with effective mass theory, with no sign of strong deepening for the Si 1s(Γ) state. We find m (P)/m (0) = 1 + (6.1 ± 0.3) × 10−3P – (1.3 ± 0.5) × 10−5P2 (P in kbar) from the CR data, after correcting for nonparabolicity via an effective two‐band k.p model. This agrees well with prior results limited to 17 kbar, and extends the measurement of m (P) in GaAs to the Γ‐X crossover.