Conductivity and hall-effect characterization of highly resistive molecular-beam epitaxial GaN layers

Highly resistive molecular beam epitaxial GaN layers are characterized by temperature dependent conductivity and Hall effect measurements. Seven n-type GaN samples with room temperature layer resistivity ranging between 8 and 4.2x10(6) Omega cm are used in this study. The experimental data are analyzed by considering various transport models such as band and hopping conduction, scattering on charged dislocations and grain boundaries controlled transport. The same defect level of 0.23 eV, attributed to nitrogen vacancy, is found for layers with rho (300)less than or equal to3.7x10(3) Omega cm. The Hall mobility for two lower resistivity layers is influenced mainly by phonon scattering (mu (H)similar toT(x), x=-1.4). However, higher resistivity layers show positive mobility power, x=0.5-0.9, which can be explained by dominating scattering on charged dislocations. Properties of layers with the highest resistivity (1x10(5) and 4.2x10(6) Omega cm) and extremely low Hall mobility (6 and <0.1 cm(2) V-1 s(-1)) are consistent with grain boundary controlled transport. The barrier height between grains of 0.11 eV and an average grain size of 200 nm are found. Neither nearest-neighbor or variable range single phonon hopping nor multiphonon hopping can be clearly attributed to the conduction of the layers investigated. (C) 2000 American Institute of Physics. [S0021-8979(00)03923-2]

Conductivity and hall-effect in highly resistive GaN layers

Highly resistive GaN layers grown by molecular beam epitaxy are characterized by temperature dependent conductivity and Hall effect measurements. Samples with rho(300) congruent to 3 x 10(3) Ohm cm show room temperature Hall mobility of 22 and 35 cm(2) V-1 s(-1) and have a temperature dependence mu(H) similar to T-x with x = 0.9 and 0.5. This is in contradiction to a sample with rho(300) congruent to 32 Ohm cm which has a room temperature mobility of 310 cm(2) V-1 s(-1) and a mu(H) similar to T-x with x = -1.4. The same activation energy of 0.23 eV, attributed to donor-like defects, is found for all three samples investigated. Temperature dependent conductivity data can be reasonably fitted considering band conduction. The presence of various hopping mechanisms is discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)02825-4]

Fabrication of a-SiGe Structure by RF Sputtering for Solar Cell Purposes

The deposition and electronic properties of a-SiGe and a-Si layers for thin-film solar cell applications are discussed. Technological parameters were developed for good layer quality of amorphous material. An inverse relation was discovered between the resistivity and the flow of hydrogen without annealing after deposition. Antimony was found to be a good doping material

Conductivity and Hall-effect in highly resistive GaN layers

Highly resistive GaN layers grown by molecular beam epitaxy are characterized by temperature dependent conductivity and Hall effect measurements. Samples with rho(300) congruent to 3 x 10(3) Ohm cm show room temperature Hall mobility of 22 and 35 cm(2) V-1 s(-1) and have a temperature dependence mu(H) similar to T-x with x = 0.9 and 0.5. This is in contradiction to a sample with rho(300) congruent to 32 Ohm cm which has a room temperature mobility of 310 cm(2) V-1 s(-1) and a mu(H) similar to T-x with x = -1.4. The same activation energy of 0.23 eV, attributed to donor-like defects, is found for all three samples investigated. Temperature dependent conductivity data can be reasonably fitted considering band conduction. The presence of various hopping mechanisms is discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)02825-4]