Sandwich structures of the form, ZnSTe/ZnSTe:Al/ZnSTe, were prepared - by means of molecular beam epitaxy - on GaAs substrates which were oriented along (100), (511) or (711). A study was thus made of the thermal diffusion of Al in a ZnS0.986Te0.014 matrix by using secondary ion mass spectroscopy depth-profiling. The relative sensitivity factor of Al with respect to Zn was 4.5 x 1019/cm3. The Al diffusion coefficients at annealing temperatures of 450 and 550C (table 12) depended upon the Al concentration. Upper and lower limits on the diffusion coefficients were obtained by using a data-fitting program which was based upon Fick’s second law. The results suggested that the diffusion was anisotropic, and this was attributed to possible channelling effects. The results also revealed that Al in the matrix was thermally stable at temperatures of up to 300C.

Secondary Ion Mass Spectroscopy Study of Al Diffusion in Sandwich-ZnSTe Structures Grown by Molecular Beam Epitaxy Z.H.Ma, T.Smith, I.K.Sou: Journal of Applied Physics, 1999, 86[5], 2505-8

 

 

Table 12

Diffusivity of Al in ZnTeS on GaAs Substrates

 

Substrate Type

Al (/cm3)

Temperature (C)

Limit

D (cm2/s)

(100)

2.13 x 1019

450

upper

3.71 x 10-15

(100)

2.13 x 1019

450

lower

5.49 x 10-16

(100)

2.13 x 1019

550

upper

4.97 x 10-14

(100)

2.13 x 1019

550

lower

6.02 x 10-15

(511)

2.11 x 1019

450

upper

3.52 x 10-15

(511)

2.11 x 1019

450

lower

7.65 x 10-16

(511)

2.11 x 1019

550

upper

4.25 x 10-14

(511)

2.11 x 1019

550

lower

7.24 x 10-15

(711)

2.18 x 1019

450

upper

3.45 x 10-15

(711)

2.18 x 1019

450

lower

9.21 x 10-16

(711)

2.18 x 1019

550

upper

3.45 x 10-14

(711)

2.18 x 1019

550

lower

5.47 x 10-15