Laser Assisted Molecular Beam Deposition of High Mobility Zinc Oxide
- PDF / 394,588 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 233 Views
0891-EE10-06.1
Laser Assisted Molecular Beam Deposition of High Mobility Zinc Oxide Meiya Li1, Nehal Chokshi2, Robert L. DeLeon2, Gary Tompa2, and Wayne Anderson1 1 University at Buffalo, Electrical Engineering Department, 332 Bonner Hall, Buffalo, NY 14260 2 AMBP Tech Corporation, 275 Cooper Avenue, Suite 112, Tonawanda, NY 14150 ABSTRACT We have utilized laser assisted molecular beam deposition (LAMBD) to deposit zinc oxide (ZnO) at room temperature. The production of ZnO films via LAMBD utilizes an excimer laser induced ablation plume of zinc in combination with pulsed oxygen gases to create a molecular beam of ZnO clusters. The deposited films have been characterized structurally and electrically in an as deposited state as well as after post deposition excimer laser annealing. The films undergo a clear structural change from a nanoparticle like film to either a microgranular film or a smooth continuous film depending upon the laser annealing power. Al ohmic contacts were made to both as-deposited and laser-annealed ZnO thin films. Thickness and refractive index, chemical composition, and surface morphology of the thin films were analyzed by using ellipsometry, electron spectroscopy for chemical analysis (ESCA), and field emission scanning electron microscopy (FESEM), respectively. Dark current-voltage (I-V), DC photo I-V, Hall-effect, and photoluminescence measurements were employed for testing the device performance. In some cases, the ZnO thin film was changed from n-type into p-type after laser annealing, and photoconductive behavior was clearly seen on the laser-annealed samples, with values of 2.8x10-4 Ω-1. Also, both samples with and without laser annealing show near-band emission at ~3.3 eV. Furthermore, the full width at half maximum (FWHM) values of the laser-annealed LAMB ZnO film was reduced from 20.02 nm or 21.68 nm to 18.2 nm when compared with that of non-laser annealed samples. This indicates that the laser annealing provided an improved stoichiometric quality and crystallinity to the ZnO thin films. INTRODUCTION Wide band-gap semiconductors such as diamond, silicon carbide (SiC), gallium nitride (GaN), and zinc oxide (ZnO) have received attention over the past decade due to a great demand to produce efficient and short-wavelength optoelectronic devices. Among them, ZnO has gained significant interest due to its large exciton binding energy (60 meV) and large bandgap of 3.37 eV at room temperature. ZnO thin films have been grown by a number of methods such as RF magnetron sputtering1, pulsed laser deposition2, molecular beam epitaxy (MBE)3, and chemical vapor deposition (CVD)4. PLD, and in particular, laser assisted molecular-beam deposition (LAMBD), has advantages compared with other techniques, such as simple experimental apparatus, capability to create high-energy source particles, and high quality film growth at low substrate temperatures5. In this paper we report fabrication and characterization of LAMBD ZnO thin films before and after laser annealing. Details about fabrication, material ch
Data Loading...
