【摘要】 本文叙述了在GaAs衬底上用有机金属气相外延(OMVPE)法生长单晶ZnSe薄膜的方法。研究了生长温度,硒锌比对外延膜光电性能的影响。发现生长温度在285℃可以得到表面光亮、结晶性好、低阻、高迁移率、深中心浓度低的外延层。以光泵浦作激发研究了OMVPE ZnSe薄膜的受激发射性质并测量其光学增益。利用ZnSe/GaAs的自然解理面形成的光反馈腔制成了激光器。该激光器的工作温度可以延续到150K。更多还原

【Abstract】 ZnSe films have been widely studied in recent years because of its potential applications as efficient blue luminescence and laser material . In this paper we present the growth and lasing characteristic of ZnSe films grown by organometallic vapor phase epitaxy (OMVPE).The dimethyl zinc (DMZn) and hydrogen selenide (H2Se) were used as zinc and selenium sources and palladium diffusion hydrogen as carrier gas. ZnSe heteroepitaxial growth was performed in a horizontal radiant -heated reactor under atmospheric pressure on GaAs (100) substrate. PL was measured at 10K under 365 nm line of a mercury arc lamp by the MM-12 monocbromator with S-1 photomultiplier.Stimulation and lasing were measured by a 44W grating monochromator with C31034 photomultiplier at 77K under 377nm line of a N2 laser with power density of 3MW/cm2.The growth temperature (Tg) is the most effective one in various growth parameters for optical and electric properties . When Tg>300℃ the surface morphology get obvious to be hillock structure with Tg increasing.Only Tg is among 250-300℃ the surface becomes smooth without hillock structure. Low resistivity ZnSe epilayers are grown in the same temperature range however high resistivity samples are obtained when Tg is beyond this temperature range. High electron mobility (300-400cm2 V-1.s-1) and low carrier concentration (1016 cm-3) are measured at room temperature in low resistivity epilayers (Fig.5). There is only one deep level located at Eg -0.33eV with the concentration of 2.4×1011cm 3 in this film measured by DLTS (Fig.6).The deep level emission of PL spectra is strongly dependent on Tg as shown in Fig.7.There are more than three kinds of deep level center in epilayers grown at the Tg of 400℃ (Fig. 7-5 ) . The photon energy of deep level emission is getting lower with the decrease of Tg. These deep levels are attributed to the dislocations natural defects donor -acceptor pair and its complexes. The Es emission is getting stronger with the increase of Tg while the deep level emission becomes stronger too. Only when Tg is near 285℃, the Es emission becomes maximum and the deep level emission becomes minimum (Fig.7-3).Stimulated and lasing emission of ZnSe epilayers were measured at different excitation density. A new band P nearby 2.765eV appears below Es approximately for 20meV under higher excitation density . It is found that the growth rate of P band intensity is much more rapidly than that of Es and its linewidth (FWHM) narrows with the increase of excitation density ( Fig. 8 and 9 ) . These experimental results show that the stimulated emission consists with P band which is ascribed to exciton-exciton scatting.The optical feedback cavity of ZnSe film was fabricated by parallel cleaved ZnSe/GaAs (100). When the pumping light beam was incident onto ZnSe surface,a blue emission with (110) orientation, a dramatic narrowing emission and a shift to longer wavelength than spontaneous emission were observed.These behaviours are characteristic of the onset of lasing. The obvious superlinear dependence of intensity on the excitation density is shown in Fig, 10 and a threshold is approximately 0.7 MW/cm2.Finally variational temperature experiments indicate that this OMVPE ZnSe laser can be operated at up to 150K.更多还原