Decomposition behaviour of nitrogen precursors for p-type doping of pyrolytic and photoassisted MOVPE of ZnSe

Work was carried out on the vapour pressure and decomposition characteristics of three possible nitrogen precursors for p-doping of ZnSe, triallylamine (TAN), trimethylsilylazide (TMSiN), and bis[di(trimethylsilyl)amido]zinc (BTM), under pyrolytic and photo-assisted conditions. The vapour pressure and room temperature stability of the nitrogen precursors was determined using an in situ ultrasonic (Epison) monitor and the results have shown that TAN and TMSiN are well behaved at room temperature with the following pressure-temperature relationship: logp(Torr) = 5.80 -1500/T and logp(Torr) = 6.78 -1513/T, respectively, both in close agreement with reported values. BTM, however undergoes decomposition in the bubbler at room temperature shown by an initial high reading on the Epison which then decreases. A mass spectrometry system was developed to quantitatively measure the decomposition of nitrogen precursors on a ZnSe surface under growth conditions of flow and temperature and this showed that TAN appears to be stable below 450 degrees C and shows no significant enhancement with photoassistance. BTM appears to undergo some decomposition to a more volatile species at room temperature and the precursor undergoes multi-step decomposition. TMSiN decomposes below 400 degrees C and shows significant photo-enhancement and is thus potentially a very good nitrogen precursor for p-type doping of ZnSe.