Invited talk abstract

It is well known that the fabrication of both low-resistivity n- and p-type wide bandgap (Eg) semiconductors is difficult (uni-polarity), because of the so called compensation and deep energy levels of the dopants in the wide bandgap semiconductors, such as GaN (Eg = 3.4 eV), AlN (Eg = 6.2 eV), and Diamond (Eg = 5.4 eV). The origin of the difficulty to fabricate the low-resistivity wide bandgap semiconductors are the compensation and the deep energy levels of dopants with increasing Eg (decreasing the dielectric constant), for example, GaN:Mg (200 meV), AlN:C (500 meV), and Diamond:P (430 meV). In order to fabricate the low-resistivity wide bandgap semiconductors, (i) we should avoid compensation with increasing solubility of the dopant, (ii) we should increase the mobility of the carriers and (iii) we should reduce the energy level of dopants by using codoping. To do so, we propose an effective new valence control method by using thermal non-equilibrium crystal growth method, which is so called the codoping method (using both n- and p-type reactive codopants at the same time), for the fabrication of low-resistivity p-type GaN, p-type AlN and n-type Diamond based upon ab initio electronic structure calculations. We discuss that the codoping increase the solubility, decrease the energy levels and increase the mobility of the carriers. We review our new valence control method of codoping for the fabrication of low-resistivity p-type GaN, AlN, and n-type Diamond. We propose the following codoping method to fabricate a low-resistivity p-type wide bandgap semiconductors (a) GaN: [Si+2Mg(or Be), H+2Mg(or Be), and O+2Mg(or Be)], (b) AlN: [O+2C]. We also review the codoping method for the fabrication of low-resistivity n-type Diamond (c) Diamond:[H+S, B+2N, H+2P]. We compare our predictions of codoping with the recent successful codoping experiments for the fabrication of the low-resistivity wide bandgap semiconductors.

References: 1) H. Katayama-Yoshida et al., Japanese Patent (Fabrication method of low resistivity p-type GaN: JP H8-258054). 2) T. Yamamoto and H. Katayama-Yoshida: Jpn. J. Appl. Phys. 36, (1997) L180. 3) H. Katayama-Yoshida and T. Yamamoto: phys. stat. sol. (b) 202, (1997) 763. 4) H. Katayama-Yoshida: Japanese Patent (Fabrication method of the low-resistivity p-type AlN: JP H10-208612). 5) T. Nishimatsu, N. Orita, H. Katayama-Yoshida: to be published in Physica B. 6) H. Katayama-Yoshida, T. Nishimatsu, T. Yamamoto and N. Orita: phys. stat. Sol. (b)210, (1998) 429. 7) H. Katayama-Yoshida, T. Nishimatsu, T. Yamamoto: Japanese Patent (Fabrication method of low resistivity n-type Diamond: JPH9-050106, JPH10-208611). 8) T. Nishimatsu, H. Katayama-Yoshida and N. Orita: Proceedings of the 24th International Conference on the Physics of Semiconductors (Edited by D. Gershoni,World Scientific, Singapore, 1999) pp.201.