Aluminum doped zinc oxide (ZnO:Al) thin films via 1.2 at. % Al content was deposited on p-type silicon wafers by using sol-gel dip coating technique to compare the effect of post treatment ambient on electrical characteristics of ZnO:Al/p-Si heterojunction. The annealing environment treatment was performed at 700 degrees C for 60 min under various gas ambients such as, air, argon, nitrogen, and vacuum. The deposited heterojunction samples were characterised in order to clarified its morphology and crystalline structure. The films showed an orientation along c-axis and the best electrical properties (0.75 x 10(-4) Omega cm) were obtained for the sample prepared in vacum. The changes in electrical properties and current-voltage performance were compared with each other after p-n junction was annealed under different ambient conditions. The heterojunction electrical parameters were determined Therefore, it was possible to make an annealing ambient comparison of the heterojunction for the cost-effect production by using sol-gel dip coating technique to use as the diode in electronic devices.