Investigation of conduction-band structure, electron-scattering mechanisms, and phase transitions in indium selenide by means of transport measurements under pressure

Abstract

In this work we report on Hall-effect, resistivity, and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic or quasihydrostatic pressure. Up to 40 kbar (ϭ4 GPa͒, the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about Ϫ98 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both three-and two-dimensional electrons, the increase rate being higher for two-dimensional electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium chloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.

Thermal hysteresis in the magnetization of the layered III-VI diluted magnetic semiconductor In1−xMnxSe

“…The III-VI semiconductors GaSe, 5,[11][12][13][14][15][16] InSe, 12,[15][16][17][18][19][20][21] GaTe, 22 and GaS ͑Refs. 23-25͒ have received considerable interest in the last few years because of their remarkable nonlinear optical properties.…”

Magnetic and transport measurements on the layered III-VI diluted magnetic semiconductor In1−xMnxSe

“…The III-VI DMSs take the form A 1−x III M x B VI . The III-VI semiconductors GaSe, [1][2][3][4][5][6][7] InSe, 3,[6][7][8][9][10][11][12] GaTe, 13 and GaS ͑Refs. 14-16͒ have received considerable interest in the last few years because of their remarkable nonlinear optical properties.…”

Transport measurements under pressure in III–IV layered semiconductors

“…For n-InSe, thermopower increases up to 4 GPa, which corresponds to the decrease of the electron concentration by nearly two orders of magnitude, due to the trapping of electrons by a deep center associated to the direct to indirect crossover in the conduction band [16]. In the case of p-InSe, the decrease of thermopower between 1 and 2 GPa correlates with the increase of the hole concentration in the same pressure range (Fig.…”

“…A 150 ton oil press was used to apply the load in the opposed anvils. A pressure of 13 GPa can be obtained routinely with this arrangement [21], which has been described in detail elsewhere [16,17]. The sample pressure was determined by the calibration of the load applied to the anvils against high-pressure resistivity transitions in calibrants like Bi, Yb, CdTe and n-type InSe [21][22][23][24][25][26][27][28], being linearly extrapolated above 10.5 GPa.…”

“…These changes of the conduction-band structure affect the transport properties of n-type InSe. Hence, research of the transport properties of n-type under compression [16,17] valuably contributed to the understanding of the pressure behaviour of the conduction-band structure of InSe.…”