The growth and diffusion of abrupt Zn profiles in un-doped, or Si-doped, material was monitored by means of secondary ion mass spectrometry. The sharp diffusion fronts which resulted from annealing treatments indicated that the Zn diffusion coefficient was concentration-dependent. The data were encompassed by the curves:

D(cm2/s) = 5.5 x 10-10 exp[-0.8(eV)/kT]

and

D(cm2/s) = 1.8 x 10-9 exp[-1.0(eV)/kT]

However, the diffusion of Zn at high concentrations appeared to be inhibited by crystal defect kinetics and resulted in a relatively concentration-independent Zn diffusion coefficient. The V/III growth ratio did not have any effect upon Zn diffusion in un-doped or Si-doped material. The diffusion of Zn in heterojunction bipolar transistor structures was different; in that the diffusion of Zn into a GaAs collector was larger by an order of magnitude, and decreased with an increase in the V/III growth ratio. In addition, the diffusion of Zn into an AlGaAs emitter was markedly lower and was inhibited by an increase in the V/III ratio. These data could be summarized by the expressions:

GaAs (V/III = 60):    D(cm2/s) = 2.0 x 103 exp[-3.0(eV)/kT]

GaAs (V/III = 120):     D(cm2/s) = 1.0 x 106exp[-3.6(eV)/kT]

Ga0.78Al0.22As (V/III = 60):     D(cm2/s) = 6.8 x 104 exp[-3.4(eV)/kT]

Ga0.78Al0.22As (V/III = 120):     D(cm2/s) = 1.1 x 10-5 exp[-1.7(eV)/kT]

P.Enquist, J.A.Hutchby, T.J.De Lyon. Journal of Applied Physics, 1988, 63[9], 4485-93