Growth Of High-quality AlN Template By MOCVD For UV Photoelectric Devices

Recently, there has been an increasing demand for AlGaN-based ultravioletphotoelectric devices such as emitters and detectors, which have many applications insolid state lighting, bioagent detection, high-density storage, short-wavelengthcommunication and UV-detection. But AlGaN layer is easy to crack due to latticemismatch and thermal mismatch between AlGaN layer and sapphire. Because of that thelattice constant of AlN is smaller than that of AlGaN, AlGaN endure compressive stresswhen it growth on AlN template avoiding cracks. So it is of great significance to realizehigh-quality AlN template for ultraviolet photoelectric devices. Using methods combiningcontinuous-flow mode and pulse-flow mode via metal organic chemical vapor deposition(MOCVD), also the intermediate temperature AlN interlayer (IT-IL) method, we obtainedhigh-quality AlN template with the full width at half maximum (FWHM) of (002) and(102) are58arcsec and544arcsec respectively.First, the influence of the flow rate of TMAl and growth pressure on the growth rateof high-temperature AlN layer is studied. The growth rate of high-temperature AlN layergrown via continuous-flow mode linearly depends on the flow rate of TMAl. However, asub-linear behavior indicating parasitic processes leading to precursor losse has beenobserved at the high-flow rate of TMAl. Besides, the growth rate of AlN layer increaseswith decreasing growth pressure due to suppression of parasitic effects, but the surface isrough.Next, the surface morphology is successfully improved combining continuous-flowmode and pulse-flow mode. Meanwhile, we obtain AlN template with high quality that theFWHM of (002) and (102) are32arcsec and662arcsec respectively and the RMS is1.8nm.Last, the tensile stress of AlN layer is relaxed via the intermediate temperature AlNinterlayer (IT-IL) method and the optimization of thickness and temperature of IT-IL. And the FWHM of (102) of AlN with no cracks at thickness of1.3μm is down to544arcsec.