Pulsed Laser Deposition of Highly Crystalline Gan Films on Sapphire
- PDF / 296,142 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 45 Downloads / 233 Views
INTRODUCTION There has been a continued interest in the growth of GaN and its alloys due to their potential applications in optoelectronics and high temperature/high power electronics[1-3]. Various modem thin film deposition techniques such as metal-organic chemical vapor deposition (MOCVD) [4], low pressure MOCVD[5], atomic layer epitaxy (ALE)[6-7], vapor phase epitaxy (VPE)[8,9], hot wall epitaxy[10] and molecular beam epitaxy (MBE) [3, 11-14].
Recently, we have reported on a novel physical vapor
deposition technique, namely, pulsed laser deposition (PLD) for growth of epitaxial GaN films [15]. In this paper we report improved growth conditions and properties of GaN films using AIN buffer layers. 343 Mat. Res. Soc. Symp. Proc. Vol. 482 ©1998 Materials Research Society
EXPERIMENTAL The deposition chamber and procedures of our pulsed excimer laser ablation setup can be elsewhere [15]. In brief, a stainless steel vacuum chamber was evacuated by a turbomolecular pump to a base pressure of lxl0"7 Torr. A KrF excimer laser ()X= 248 nm, " = 30 ns) was used for ablation of a polycrystalline, stoichiometric GaN target either prepared from commercialy available GaN powder or CVD grown bulk gray colored GaN. The energy density used for target ablation was - 1-2 Jcm-2. The ablated material was deposited on a sapphire(0001 ) substrate kept at a distance of -7 cm from the target 3 surface in an NH ambient background gas pressure varying from 10-5 Torr. Before GaN was deposited, thin layers of AIN were grown by in-situ PLD by ablating AIN target. 0.5-1 jim thick films were grown 0 at a rate of -1 jim/hr. The GaN films were deposited at 750 C. The crystalline quality of the GaN layers
was evaluated using the four-circle x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and ion channeling techniques. We also report on detail studies of surface morphology, optical properties, and electrical resistivity of the PLD GaN films. RESULTS AND DISCUSSION 2 105 ................. ..................
;F• (a) (a)
1.51
a)
"•
0).
°-
c
c
10
c
S:1.5
04
105•-
c
.
•
O
.0q
510'4 ,_,_0 JI
20
2. .
40
1 105
ca
104
•
:a)0
o
CL
z
a
caaC/a
___..................0.
60
,0
Data Loading...
