Effect of ammonia flow rate on impurity incorporation and material properties of Si-doped GaN epitaxial films grown by reactive molecular beam epitaxy

Effect of ammonia flow rate on the impurity incorporation and material prop erties of Si-doped GaN films grown by reactive molecular beam epitaxy (RMBE ) process is discussed. It appears that the ammonia flow rate has a margina l effect on the incorporation of impurities into the Si-doped GaN films exc ept there was a little decrease in O and Si with increasing ammonia flow ra te when the Si concentration in the film is higher than 10(18) cm(-3). Elec tron Hall mobility of Si-doped GaN films grown by RMBE varies with ammonia flow rate used during film growth. From deep level transient spectroscopy ( DLTS) measurements for Schottky diodes grown with different ammonia flow ra tes, one deep trap (C1) particular to the RMBE films was found. The concent ration of C1 trap was found to be the lowest in the sample grown with the c ondition leading to the highest electron Hall mobility within the scope of this experiment. In addition to the DLTS result, other characterization tec hniques used (x- ray diffraction, cross-sectional transmission electron mic roscopy, and low-temperature photoluminescence! also consistently show that the RMBE process requires certain value of ammonia flow rate (or V/III rat io if the Ga flux is fixed! to produce Si-doped GaN films with high quality . (C) 1998 American Institute of Physics. [S0021-8979(98)04124-3].