Direct Growth of AIN Thin Layer on (111)Si Substrate by RF-MBE
- PDF / 1,438,528 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 2 Downloads / 222 Views
ABSTRACT The nitridation process of (I 11)Si surface has been studied by in-situ reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) measurements. It has been clarified that the nitridation of the Si surface is occurred even if the shutter of the discharged if-plasma gun is closed. The growth process of AIN epilayer on the Si substrate by migration enhanced epitaxy (MEE) has been investigated by in-situ RHEED and atomic force microscopy (AFM) observations. It has been found that the AIN epilayer is directly grown on (11 )Si by MEE growth. INTRODUCTION Many GaN-based applications of optoelectronic and electronic devices have been demonstrated on sapphire and SiC substrates [1-5]. Devices formed on Si substrate, however, have not yet been performed regardless of many advantages of Si such as high quality, large size, low cost and controllability of conductivity [6-121. S. Guha and N. A. Bojarczuk reported that it is necessary for the realization of GaN-based devices on Si to suppress the nitridation of the surface of Si substrate [7]. There is, however, a little work on the nitridation process of Si substrate [13]. Si substrate is mismatched with GaN in lattice constant and thermal expansion coefficient as sapphire. Therefore, it has been expected to grow a high quality GaN epilayer on Si using an appropriate buffer layer. An AIN thin layer has a potentiality of the buffer layer [14,15]. However, the initial growth process of thin AIN layer on Si substrate has not been clarified. In the present work, we have investigated the nitridation process of Si surface, the direct growth process of thin AIN layer on (11 1)Si substrate by migration enhanced epitaxy (MEE) method.
405
Mat. Res. Soc. Symp. Proc. Vol. 512 ©1998 Materials Research Society
EXPERIMENT A growth chamber equipped with a RHEED system was used for in-situ observations of AIN epilayers on (111 )Si substrates. Figure 1 shows a schematic drawing of the growth chamber apparatus. The growth chamber was evacuated by an oil diffusion pump with a liquid N2 trap to a base pressure of 2x10 1 ° Torr. (11 1)Si wafers were used as substrates. They were chemically cleaned with etching by dipping in a solution of HC1 : H202 : H20 = 1 : 1 : 6 before being set in the preparation chamber. The Si substrate had a 7x7 reconstructed surface structure after thermal cleaning at a substrate temperature of 850 TC for 10 min. The substrate temperature was measured by an optical pyrometer which was corrected using the Al melting point. The thin AIN layers were deposited on the substrates at 500 °C by MEE method under the condition of a N2 flow rate of 0.2 sccm, a radio frequency (rf) plasma power of 200W, and an Al flux of 5x108 Torr. The pressure under irradiation of if-plasma enhanced nitrogen (N*) gas was 1.2x 104 Torr. The substrate surface and the initial growth processes of AIN layers were in-situ observed by RHEED system operated at an acceleration voltage of 15kV. The morphology of the substrate and the growing surfaces was proved by A
Data Loading...
