Impurity band conduction

The literature abounds with reports of thermal activation energies for shallow donors in GaN, obtained from Hall effect measurements over a range of temperatures, above and below room temperature, though their interpretation is rendered problematic by a number of complicating factors. At low temperatures there is clear evidence for impurity band conduction (see, for example, [31]) which severely limits the temperature range over which data may usefully be fitted to the standard equation for free carrier density n in terms of the donor density ND and compensating acceptor density NA ... 

The central problem in the study of ionic conduction is to discover the details of the atomic transport processes involved in the growth of films. This will be discussed in the first part of this review. The electronic conductivity is of considerable theoretical interest and is of great practical importance for microelectronic devices. We discuss the system in which a thin metal counterelectrode replaces the electrolyte solution in which the oxide was made. Thermionic and field assisted emission, tunneling processes, impurity band conduction, and space-charge limited currents, have to be considered. We shall draw on results for oxide films made by other processes, such as evaporation and thermally promoted reaction with oxygen. 

Hickmott has discussed the possible mechanisms in considerable detail. The tentative theory which he has advanced is, briefly, that the production of conductivity in the forming process is due to the development of impurity-band conduction, in a concentrated band of impurity states which are ionized in the forming process. The current is then space-charge limited. The impurity-band nature of the conduction is supposed to account for the small temperature dependence. To account for the negative resistance it is supposed that as the field is increased the impurity-band states are filled by electrons tunneling from valence band or lower impurity states. The process involved in the development of the impurity band conduction is somewhat uncertain. 

Conwell EM (1956) Impurity band conduction in germtmium and silicon. Phys Rev 103 51-61... 

At high temperatures p approaches the saturation value Na N at low temperatures p Na or Nu and, provided the acceptor concentration is sufficiently low to avoid impurity band conduction, Eq. (1) approximates to... 

The InfraRed Array Camera (IRAC) provides imaging at shorter wavelengths with bands centered at 3.6, 4.5, 5.8 and 8.0 /txm. The 3.6 and 4.5 fim bands utilize two 256 X 256 pixel In Sb detector arrays while the two longer bands utilize 256 x 256 pixel Si As impurity band conduction detectors. Although there are four photometric bands IRAC has only two entrance apertures. Dichroic beam splitters allow the 3.6 and 5.8 band to share one aperture while the 4.5 and 8.0 bands share the other. This doubles the efficiency for multiband observations. 

Key words Infrared Focal Plane Array - Impurity Band Conduction - Space Astronomy... 

Two 256X256-pixel arsenic-doped-silicon (Si As) impurity band conduction (IBC) hybrid detector arrays developed by Hughes Technology Center have been evaluated for space-based astronomy applications. Potential applications include instrumentation on orbiting astronomy platforms such as the Space Infrared Telescope Facility (SIRTF). 

Fowler, A. M. and Joyce, R. R. 1990, Status of the NOAO Evaluation of the Hughes 20x64 Si As Impurity Band Conduction Array , SPIE Instrumentation in Astronomy VII, 1235... 

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