The electron transport that occurs within wurtzite zinc oxide and the application of stress
- PDF / 344,700 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 41 Downloads / 176 Views
The electron transport that occurs within wurtzite zinc oxide and the application of stress Poppy Siddiqua1, Michael S. Shur2, and Stephen K. O’Leary1 School of Engineering, The University of British Columbia, Kelowna, British Columbia, Canada V1V 1V7 2 Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180-3590, U.S.A. 1
ABSTRACT We examine how stress has the potential to shape the character of the electron transport that occurs within ZnO. In order to narrow the scope of this analysis, we focus on a determination of the velocity-field characteristics associated with bulk wurtzite ZnO. Monte Carlo simulations of the electron transport are pursued for the purposes of this analysis. Rather than focusing on the impact of stress in of itself, instead we focus on the changes that occur to the energy gap through the application of stress, i.e., energy gap variations provide a proxy for the amount of stress. Our results demonstrate that stress plays a significant role in shaping the form of the velocity-field characteristics associated with ZnO. This dependence could potentially be exploited for device application purposes. INTRODUCTION Zinc oxide (ZnO), a II-VI compound semiconductor, has become a recent focus of attention for the materials research community [1]. While traditional forms of this material, prepared as powders or in oriented polycrystalline form, were quite defective in nature, highquality bulk wurtzite ZnO crystals are now available for device application purposes [2]. As a consequence, the range of device applications being considered for this material has dramatically increased. ZnO possesses a number of interesting material properties, including a wide and direct energy gap, an elevated polar optical phonon energy, and a wide conduction band inter-valley energy separation. This combination of material properties suggests that ZnO will exhibit superb electron transport characteristics [3]. This supposition has been confirmed through the use of Monte Carlo electron transport simulations [4,5]. This has led some to speculate that ZnO could potentially be used as a material for high-power and high-frequency device applications, potentially serving as a competitor to the other wide energy gap semiconductors that are being considered for such applications, such as gallium nitride and silicon carbide [6]. Through an examination of the sensitivity of the electron transport characteristics associated with ZnO on the non-parabolicity of the lowest energy valley in the conduction band, it was demonstrated that ZnO is more sensitive to variations in the non-parabolicity coefficient than other comparable compound semiconductors [7]. It was proposed that this sensitivity could be exploited for device applications. Stress resulting, for example, from pseudomorphic growth on a heterogeneous substrate and due to differences in the thermal expansion coefficients between the substrate and epitaxial materials, has the potential to change the band structure in a
Data Loading...
