TY - JOUR
T1 - Effects of Ar vs. O2 ambient on pulsed-laser-deposited Ga-doped ZnO
AU - Scott, Robin C.
AU - Leedy, Kevin D.
AU - Bayraktaroglu, Burhan
AU - Look, David C.
AU - Zhang, Yong-Hang
N1 - Funding Information:
Most of the experimental work was carried out at the Air Force Research Laboratory, Wright-Patterson AFB, Dayton, OH. The work of RCS and YHZ was partially supported by Science Foundation Arizona , Contracts SRG 0190-07 and SRG 0339-08 , and by the Air Force Research Laboratory/Space Vehicles Directorate , Contract FA9453-08-2-0228 and AFOSR Grant FA9550-10-1-0129 . The work of DCL was partially supported by AFOSR Grant FA9550-10-1-0079 (K. Reinhardt) and NSF Grant DMR0803276 (L. Hess). The authors thank T.A. Cooper and W. Rice for the Hall-effect and PL measurements, respectively. We also thank Vijay D'Costa for spectroscopic ellispometer measurements and modeling. We acknowledge the use of facilities at the LeRoy Eyring Center for Solid State Science, Arizona State University.
PY - 2011/6/1
Y1 - 2011/6/1
N2 - Ga-doped ZnO films were deposited by pulsed laser deposition (PLD) at 200 °C and 10 mTorr in either pure argon (Ar films) or in oxygen (O2 films). The bulk resistivity of the Ar films is <2×10-4 Ω cm at 300 K, two orders of magnitude lower than that of the O 2 films. In the Ar films, the donor concentration ND as determined by a detailed Hall-effect analysis is close to 100% of the total Ga concentration [Ga] measured by secondary ion mass spectrometry (SIMS), while in the O2 films ND is less than 50% of [Ga]. Furthermore, the compensation ratio K=NA/ND is >90% for the O 2 films and <60% for the Ar films. Yet, when the oxygen pressure is reduced to 0.2 mTorr, the O2 films have resistivities of about 5×10-4 Ω cm, approaching those of the Ar films. These results suggest that oxygen-rich environments produce Ga/O complexes that reduce the dopant activation efficiency and thus decrease ND and increase K. Some of these complexes may also contribute to the increase in deep centers observed in photoluminescence.
AB - Ga-doped ZnO films were deposited by pulsed laser deposition (PLD) at 200 °C and 10 mTorr in either pure argon (Ar films) or in oxygen (O2 films). The bulk resistivity of the Ar films is <2×10-4 Ω cm at 300 K, two orders of magnitude lower than that of the O 2 films. In the Ar films, the donor concentration ND as determined by a detailed Hall-effect analysis is close to 100% of the total Ga concentration [Ga] measured by secondary ion mass spectrometry (SIMS), while in the O2 films ND is less than 50% of [Ga]. Furthermore, the compensation ratio K=NA/ND is >90% for the O 2 films and <60% for the Ar films. Yet, when the oxygen pressure is reduced to 0.2 mTorr, the O2 films have resistivities of about 5×10-4 Ω cm, approaching those of the Ar films. These results suggest that oxygen-rich environments produce Ga/O complexes that reduce the dopant activation efficiency and thus decrease ND and increase K. Some of these complexes may also contribute to the increase in deep centers observed in photoluminescence.
KW - A3. Pulsed laser deposition
KW - B1. Transparent conductive oxide
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U2 - 10.1016/j.jcrysgro.2011.03.002
DO - 10.1016/j.jcrysgro.2011.03.002
M3 - Article
AN - SCOPUS:79957840275
SN - 0022-0248
VL - 324
SP - 110
EP - 114
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
IS - 1
ER -