J. Kocka et al., A-SIH ELECTRON-DRIFT MOBILITY MEASURED UNDER EXTREMELY HIGH ELECTRIC-FIELD, Physical review. B, Condensed matter, 45(12), 1992, pp. 6593-6600
The electron drift mobility of undoped a-Si:H is studied by a current
time-of-flight method over a broad temperature range (T = 35-300 K). A
possibility of deducing the drift mobility (mu(D)) from the initial (
t = 0) value of space-charge-limited current (SCLC) is suggested and v
erified for T > 120 K. In the SCLC case an effect, the so-called pseud
otransit, is observed and explained. The drift mobility is deduced at
electric fields F > 1 x 10(5) V/cm and low temperatures, T < 120 K, no
t only for a high intensity of illumination (the SCLC case) but also f
or the "small-signal" case (low-intensity illumination). Both these va
lues are in agreement, and there is no increase of mu(D) at T < 100 K,
as observed by W. E. Spear [in Amorphous Silicon and Related Material
s, Advances in Disordered Semiconductors Vol. 1, edited by H. Fritzsch
e (World Scientific, Singapore, 1989), p. 721]. The strong electric-fi
eld dependence of the collected charge is observed at these temperatur
es and even at 40 K almost full charge collection is reached. This imp
lies that the quantum efficiency eta almost-equal-to 1. In the end, tw
o possibilities of explaining the discrepancy in comparison with Spear
's work are discussed.