Very high two-dimensional hole gas ͑2DHG͒ drift mobility of 3100 cm 2 / V s is obtained at extremely high density of 41ϫ 10 11 cm −2 in the modulation doped, 20 nm thick, strained Ge quantum well ͑QW͒ of SiGe heterostructure at room temperature. Very high 2DHG density is achieved by increasing the boron modulation doping, reducing the spacer layer thickness located between it and Ge QW, and increasing the valence-band offset of Ge QW, which also results in the enhancement of mobility. The obtained 2DHG mobility and carrier density exceed those reported for two-dimensional electron gas in the strained Si QW of SiGe heterostructures.

CuInSe2 films with Cu/In ratios of m=0.83–0.99 have been deposited on glass substrates by the co-evaporation method using a bi-layer process. The effects of sodium in these films have been investigated by comparing the electrical and optical properties of the films with and without the Na2Se incorporation. Two donor-acceptor pair emissions, [D, A]α at 0.89–0.94 eV and [D, A]β at 0.84–0.87 eV, were typically observed in the photoluminescence spectra. The relative intensity of [D, A]α to [D, A]β was found to depend strongly on both the Cu/In ratio and Na incorporation. For the films with m=0.94, [D, A]α was predominantly observed regardless of Na incorporation. For m≤0.90, [D, A]β became dominant for the films without Na, while [D, A]α remained as the dominant emission for the films with Na. A correlation between the prominence of [D, A]α and resistivities below 2×103 Ω· cm was found, suggesting a reduced compensation by suppressed Se vacancy donors due to the presence of Na.

CuIn3Se5 films have been deposited with Na2S on Coning 7059 glass substrates by the two-stage co-evaporation method. Stoichiometric CuIn3Se5 films with p-type conduction with the resistivities of 106 Ω·cm range were obtained by our sodium control technique. Enhanced grain growth and preferred (112) orientation were also clearly observed with sodium incorporation; the same effect that has been reported for chalcopyrite CuInSe2 thin films. The effects of sodium in these films have been investigated by comparing the electrical and optical properties of CuIn3Se5 films with and without the Na incorporation. A correlation between the photoluminescence spectra and the resistivity or conduction type of the CuIn3Se5 films was found, suggesting a reduction in compensation due to the suppression of donor-type defects by the presence of Na.

The room-temperature two-dimensional hole gas ͑2DHG͒ conductivity as high as 649.3 S is obtained by implementation of double-side modulation doping ͑DS-MOD͒ of an 8 nm thick strained Ge quantum well in a SiGe heterostructure. This conductivity is about three times higher than that of the conventional SiGe heterostructure with single-side modulation doping ͑SS-MOD͒. While the low-temperature ͑T =3 K͒ mobility with DS-MOD is two times higher than that with SS-MOD, the room-temperature mobility of the two is practically the same, suggesting that phonon scattering is the dominant limiting mechanism at the device operating temperatures.

Carrier transport properties were investigated for polycrystalline silicon (poly-Si:H:F) films fabricated at 300 °C by 100 MHz plasma enhanced chemical vapor deposition from gaseous mixture of SiF4 and H2. Analysis of free carrier optical absorption (FCA) revealed that 1 μm thick (400) oriented phosphorus-doped poly-Si:H:F films with a carrier concentration of 5×1019 cm−3 had the average electron mobility in crystalline grains at 40 cm2/V s, while the electron mobility of the (220) oriented phosphorus-doped poly-Si:H:F films was only 12 cm2/V s. These results indicated that (400) oriented poly-Si:H:F films had excellent quality crystalline grains. Analyses of the FCA combined with Hall effect current measurements revealed that the electrical conductivity at grain boundaries of top doped films increased as the underlying film thickness increased from 0 to 280 nm for (400) oriented phosphorus-doped/undoped double layered samples, but grain boundaries still acted as large resistive regions limiting the effective conductivity.