【摘要】 获得高质量的ｎ型ＧａＮ单晶膜是制作ＧａＮ基光电子器件的关键之一。采用立式ＭＯＣＶＤ系统生长ＧａＮ：Ｓｉ单晶膜，通过优化生长工艺，获得了电子载流于浓度高达２ ×１０１９ｃｍ－３，迁移率达１２０ｃｍ２／Ｖ·ｓ的ｎ型ＧａＮ：Ｓｉ单晶膜；并有效地抑制了ＧａＮ中由深能级引起的黄带发射，大大提高带边发光强度。研究结果还表明：随着Ｓ掺杂量的增大，ＧａＮ：Ｓｉ单晶膜的电子载流于浓度增加，迁移率下降，Ｘ光双晶衍射峰半高宽增大。首次报道了随掺Ｓ量增大，ＧａＮ：Ｓｉ单晶膜的生长速率显著下降的现象。更多还原

【Abstract】 Si-doped GaN was grown by MOCVD method using a home-made vertical reactor operating at atmospheric pressure. To prevent parasitic reactions in the gas phase, reagents were mixed at 20mm before reaching the substrate. The growth was carried out on (0001 ) oriented sapphire substrates using Trimethylgallium(TMGa) and blue-ammonia(NHs) as Ga and N sources, respectively. The doping reagents was the diluted silane(SiH4). The mixed gases of hydrogen and nitrogen were used as the carrier gases. A thin buffer layer with thickness of about 15um was grown at 520℃ and recrystallized at 1 060℃for 6 minutes. The Sidoped GaN films were grown at 1 060℃with the [ V ]/[ Ⅲ] ratio of 1 000: 1 The growth time was an hour with the growth rate in the rage of 1. 8 - 4. 0 um/h. The photoluminescence (PL ), the Van der Pauw Hall method, and the double-crystal X-ray diffraction(DXRD) were used to measure the optical, electrical, and structural data of these films at room temperature. Table 1 is the characterization data of the Si-doped GaN films. Fig. 1 shows the electron carrier concentration and mobility of Si-doped GaN as a function of SiH4/ TMGa ratio. The carrier concentration varies between 1 ×1017 and 4 ×1019cm - 3. The relationship between the carrier concentration and the flow rate ratio of SiH4/TMGa is approximately linear. Fig. 2 shows the photoluminescence (PL) spectra of Si-doped GaN as a function of the SiH4/TMGa ratio at 300K. The excitation-source was a 15mW He-Cd laser. The band-edge emission and deep-level emission were observed around 370um and 550um, respectively. Very strong band-edge emission without yellow band(limited by the apparatus)was observed in Fig. 2-D. Fig.3 shows the intensity of band-edge emission, the intensity ratio between band-edge emission and deep-level emission as a function of the carrier concentration of Si-doped GaN films. The intensity of bandedge emission was highly enhanced and the intensity of yellow emission was restrained with the increasing ofcarrier concentration. As shown in Fig. 3, Si-doped GaN films, with carrier concentration of 2 ×1019cm-3 were obtained. For this kind of film, the intensity of band edge emission is as high as one hundred times of that of unintentional doped GaN and no yellow luminescence can be found. Fig.4 shows the relationships between the SiH4/TMGa ratio and the FWHM of double-crystal x-ray diffraction (DXRD ) and the growth rate of Si- doped GaN films. The FWHM of DXRD of GaN films became wider when SiH4/TMGa ratio increased. However, the growth rate decreased from 4 um/h to 1 .7um/h with increasing SiH4/TMGa ratio. This phenomenon has not been reported to our knowledge. In this paper, Si-doped GaN films with carrier concentration of 2 ×1019 cm-3, electron mobility of 120.m2/V.s can be obtained. FOr this kind of film, FWHM of the band edge emission at room temperature is only 60meV, and no yellow emission can be observed. In this work, the optimum flow ratio of SiH4/TMGa was 2 ×10 -4.更多还原