Dependencies of low-temperature electronic properties of MBE-grown GaAs AlGaAs single heterojunctions upon arsenic species

'We have grown delta-doped high electron mobility transistor (HEMT) structu re by usual solid source molecular beam epitaxy (MBE) with As-4 and As-2 an d found highest low-temperature electron mobility of similar to 2 x 10 degr ees cm(2)/V s for the growth temperature, T-g = 640 degrees C and for the A s cracking temperature, T-c = 800 degrees C. which is rather an As-2-domina nt condition. Room-temperature Hall measurements for the undoped GaAs films suggested that a conduction-type transition occurs at certain T-c(T-c,T-tr ) and it gradually rises as T-g increases. PL estimations for the GaAs samp les suggested that total impurity(donor + acceptor) density decreases sudde nly almost at the T-c just before the p/n transition and that donor density slightly increases as T-c is increased. It is also presumed from far-infra red photoconductivity (FIRPC) measurements that residual donor density is i ncreased by increasing T-c and it is decreased by increasing T-g for the fi xed T-c of 950 degrees C. Those results suggest that the growth condition f or the lowest impurity (most intrinsic) GaAs film would give the condition of obtaining highest low-temperature electron mobility in the heterojunctio n. (C) 1999 Elsevier Science B.V. All rights reserved.