Structural and optoelectronic properties of indium-dopeda-Ge:H thin films

Abstract

This work reports on the structural, optical, and transport properties of rf sputtered In-doped hydrogenated amorphous germanium thin films. It has been found that the incorporation of In induces important changes in the optoelectronic properties of the Alms. The experimental results may be explained in terms of acceptor levels produced by tetrahedrally coordinated In, in a way similar to In doping of c-Ge. The transition from n-type conduction of as-deposited samples to p-type conduction has been monitored through thermopower measurements. Indium concentrations of the order of 1'Po induce the pinning of the Fermi energy at 0.45 eV above the valence band edge and a thermally activated conductivity at room temperature having an activation energy of a few meV. The eKect is explained in terms of nearest-neighbor hopping between electron states produced by In atoms in a metal-like coordination at defective sites of the Ge network.

Deposition of microcrystalline Ge films using hot-wire technique without toxic gases

“…4 shows Raman spectra for the films deposited on Si and Corning substrate with the substrate temperature as a parameter. The all films, except the films deposited on Corning substrate at T s = 200°C, showed the sharp peak at about 300 cm À1 and the small shoulder peak at about 280 cm À1 due to crystalline and amorphous Ge, respectively [12,13]. This indicates that the films were microcrystalline Ge films.…”

“…On the other hand, the films deposited on Corning substrate at T s = 200°C showed the peak at about 280 cm À1 only. This indicates that the film was amorphous Ge film [12].…”

Bismuth doping of hydrogenated amorphous germanium thin films

“…[13,14]. Thermopower data indicate that Bi impurity always induces a dominant electron conduction, implying an n-type doping, as expected from a column V element [11].…”

“…The doping was performed by co-sputtering small, solid pieces of Bi together with the Ge target. Details on sample deposition parameters and film characterization are given in previous publications of the Campinas group [13,14]. Films of 10 − 4 cm typical thickness were deposited onto Corning 7059 glass and onto crystalline silicon substrates.…”

Steady-state photoconductivity of gallium- and indium-doped hydrogenated amorphous germanium thin films

“…[2][3][4][5] As part of this research effort, n-and p-type doping studies of a-Ge:H have been undertaken by our group, using different elements of columns III and V of the Periodic Table as dopant species. [6][7][8][9][10][11][12][13] The measurement of the photoconductivity ͑PC͒ is a valuable tool to investigate the recombination processes and the distribution of deep defect states in the mobility gap of amorphous semiconductors. In particular, the dependence of the PC on the position of the Fermi level (E F ) in doped samples, provides information on the recombination processes of electrons and holes, as E F moves toward the band edges.…”