from amorphous to crystalline phase in the GaN film [12]. The formation of a-GaN/Si(111) isotype heterojunction in this work was thereafter characterized in term of current-voltage (I-V) characteristic ((Fig. 2.2 (i)) at room temperature. It was observed that rectification behavior has been demonstrated for the isotype heterojunction. Therefore, further investigation was carried out by analyzing Schottky behaviors of the heterojunction via forward bias I-V measurement using nickel (Ni) ((Fig. 2.2 (ii)(a)) and chromium (Cr) ((Fig. 2.2 (ii)(b)) as the Schottky contacts ((Fig. 2.2 (ii)).
The calculated Schottky barrier height values were 0.62 and 0.64 eV,
respectively for the Ni/a-GaN and Cr/a-GaN Schottky barriers. These results have inevitably contributed certain innovation for further exploration and development of low temperature grown GaN films for use in electronic and optoelectronic applications [12].
(i)
(ii)
Fig. 2.2 (i) I-V characteristics for a-GaN/Si(111) isotype heterojunction grown at 200ËšC and (ii) Forward bias I-V characteristics of (a) Ni/a-GaN and (b) Cr/a-GaN Schottky barriers [12].
Besides a-GaN/Si(111) isotype heterojunction, the a-GaN film was also grown on p-type Si(111) substrate via ECR plasma-assisted MOCVD technique to form anisotype (n-p) heterojunction.
I-V characterization for the a-GaN/p-Si(111) anisotype heterojunction [13] 4