IODINE DOPING IN ZNSE FILMS GROWN BY VAPOR-PHASE EPITAXY

Properties of ZnSe films doped with iodine impurities were investigate d. The ZnSe films in most cases were grown at 350-degrees-C by using m etallic zinc and selenium as the source materials; their vapors were t ransported separately by H-2 gas under atmospheric pressure. CH3I (9.4 ppm, diluted in helium) was used as a dopant source. Epitaxial growth occurred when the flow rate of CH3I was below 0.025 mumol/min. The el ectron concentration could be controlled in the range 5 X 10(16)-7 X 1 0(17) cm-3, which was proportional to the dopant flow rate between 0.0 021 and 0.016 mumol/min. In a film grown at 300-degrees-C, the electro n concentration reached 4.4 X 10(18) cm-3. A high quality PL property was observed for the film grown with the minimum flow rate of CH3I. Wh en the [Se] to [Zn] flow rate ratio was varied from 0.69 to 3.53 at a constant CH3I flow rate of 0.0042 mumol/min, the deep-level emission a lmost disappeared above [Se]/[Zn] = 2.2. The value of full width at ha lf maximum of the (600) Cu Kalpha X-ray diffraction peaks showed its m inimum at the same flow rate ratio. Two-step doping of iodine was also attempted to obtain the optically and electrically desirable ZnSe fil m as a blue-emission layer. SIMS analysis confirmed that the ZnSe film with a two-step iodine concentration was indeed grown.