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

The effect of hydrostatic pressure ( P ) on the k = 0 conduction band mass m   0 * ( 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 d E /d B 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   0 * ( P )/m   0 * (0) = 1 + (6.1 ± 0.3) × 10 −3 P – (1.3 ± 0.5) × 10 −5 P 2 ( 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   0 * ( P ) in GaAs to the Γ‐X crossover.