Growth of non-polar a -plane and cubic InN on r -plane sapphire by molecular beam epitaxy
- PDF / 170,577 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 40 Downloads / 205 Views
Y12.6.1
Growth of non-polar a-plane and cubic InN on r-plane sapphire by molecular beam epitaxy Hai Lu, William J. Schaff and Lester F. Eastman Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 Volker Cimalla, Joerg Pezoldt and Oliver Ambacher Center for Micro- and Nanotechnologies, Technical University Ilmenau, PF100565, 98693 Ilmenau, Germany J. Wu, Wladek Walukiewicz Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
ABSTRACT Growth of non-polar III-nitrides has been an important subject recently due to its potential improvement on the efficiency of III-nitride-based opto-electronic devices. Despite study of non-polar GaN and GaN-based heterostructures, there are few reports on epitaxial growth of non-polar InN, which is also an important component of the III-nitride system. In this study, we report heteroepitaxial growth of non-polar InN on r-plane sapphire substrates using plasma-assisted molecular beam epitaxy. It is found that when a GaN buffer is used, the following InN film appears to be non-polar (11 2 0) a-plane which follows the a-plane GaN buffer. The room temperature Hall mobility of undoped a-plane InN is around 250 cm2/Vs with a carrier concentration around 6×1018 cm-3. Meanwhile, if InN film is directly deposited on r-plane sapphire without any buffer, the InN layer is found to consist of a predominant zincblende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase with increasing content with proceeding growth.
INTRODUCTION Growth of non-polar wurtzite III-nitrides has been an important subject recently due to its potential improvement on the efficiency of III-nitride-based opto-electronic devices. Commercially available GaN-based light-emitting diodes (LEDs) are most commonly grown on (0001) Al2O3 or 6H-SiC substrates. The as-grown films or heterostructures feature the polar (0001) orientation, and hence a strong built-in electrostatic field can exist in the active layers because of the spontaneous and piezoelectric polarizations.[1] The presence of the polarization field is unfavorable for light generation since it gives rise to a significant band bending, and thus reduces the overlap of electron-hole wave functions in quantum wells. In addition, the electricfield-induced quantum confined stark effect causes an undesirable redshift in the emission spectra.[2]. Two useful approaches for reducing the deleterious effects of the build-in field are to grow wurtzite III-nitrides along the non-polar direction or to grow cubic III-nitrides. These considerations already led to a number of successful attempts at growing non-polar wurtzite GaN and cubic GaN.[3,4] The absence of built-in electrostatic fields has been demonstrated in GaN/AlxGa1-xN multiple quantum wells (MQWs) grown on r-plane sapphire by molecular beam
Y12.6.2
epitaxy (MBE). The (11 2 0) MQWs show much stronger photoluminescence compared with (0001) MQWs.[5] However, despite the intensive studies on non-polar GaN films and GaN-based heterostr
Data Loading...
