Space-charge controlled conduction in low-temperature-grown molecular-beam epitaxial GaAs

Abstract

Current transport in low-temperature (LT) molecular-beam epitaxial GaAs grown at 200-300 °C on an n+ GaAs substrate is studied by means of current–voltage–temperature characteristics. The resistivity of LT GaAs at low electric fields is ρ⩾108 Ω cm, much higher than resulting from van der Pauw measurements. It is found that the measured resistivity decreases with increasing the LT GaAs thickness. This is explained by space-charge effect in the vicinity of n+/LT GaAs junction and subsequent suppression of hopping conduction in the high-field junction region.

On the thermal dependence of the generation of terahertz radiation by photomixing

“…The increased absorption coefficient due to the shift of bandgap will lead to a localization of carrier generation closer to the surface and the resulting increase in collection efficiency might provide the leverage for a superlinear increase in photocurrent with absorption coefficient. In addition, it seems possible that the enhancement of hopping conductance at elevated temperatures demonstrated for the dark current [17,18] affects also the transport processes under illumination.…”

“…The dark current increases for increasing temperature as expected for a semiconductor material. In LT-GaAs the main contribution is believed to be the activation of hopping conduction between As precipitates [17,18]. Between 17…”

Ultrafast Phenomena in Freestanding LT-GaAs Devices

“…• C with a growth rate of about 1 µm/h [3,6]. After the MBE deposition, wafers with LT-GaAs layers were annealed in situ at 600…”

“…7 Ω cm) [2], high breakdown electric field (> 300 kV/cm) [2], and relatively large mobility (∼ 150 cm 2 /(V s)) [3]. These properties make LT-GaAs the material of choice for fast and sensitive photodetectors [4][5][6][7][8][9][10][11][12][13][14] and photomixers [15][16][17][18][19][20].…”

“…• C [3,6]. Artificially created deep-level traps are responsible for the very short carrier lifetime in LT-GaAs based opto--electronic devices.…”