Growth of GaN, AlN and InN by Electron Cyclotron Resonance-Metal Organic Molecular Beam Epitaxy
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GROWTH OF GaN, AIN AND InN BY ELECTRON CYCLOTRON RESONANCEMETAL ORGANIC MOLECULAR BEAM EPITAXY P. W. WISK*, C. R. ABERNATHY*, S. J. PEARTON*, F. REN*, J. R. LOTHIAN*, A. KATZ*, AND K. JONES**
*AT&T Bell Laboratories, Murray Hill, NJ 07974 **University of Florida, Gainsville, FL ABSTRACT
We have investigated the feasibility of depositing GaN, AIN and InN from nitrogen plasmas by electron cyclotron resonance-metal organic molecular beam epitaxy (ECRMOMBE). Growth rate, morphology, and resistivity were evaluated as function of growth temperature and group 11 flux. It was found that stoichiometric materials could be deposited at reasonable growth rates on either GaAs or sapphire substrates. Low contact resistance, -5x 10-7 a-cmM, can be obtained on In due to the high carrier concentrations, 1020 cm- 3 obtained in this material.
INTRODUCTION The potential for using the Group III nitrides (InN, GaN, and AIN) and their ternary counterparts for wide band gap optical devices, operating in the red to the ultra-violet, has received considerable attention [1]. Previously, sputtering [2,3] or MOCVD [4] have been used to obtain reproducible nitride films. The large quantities of NH 3 or similar gases that are used in these techniques are not compatible with most UHV pumping systems therefore, growth of these materials by MOMBE has not been studied extensively. However, with the recent development of UHV compatible plasma sources, the incorporation of nitrogen can be made much more efficient through the generation of nitrogen atoms in situ. Electron cyclotron resonance (ECR) plasma sources are more generally preferred as power sources rather than radio frequency (RF) sources because of their low ion energies. While nitride growth by ECR-MBE has been investigated by several groups [4,5,6], little is known about growth of InN, GaN and AIN using electron cyclotron resonance-metal organic molecular beam epitaxy (ECR-MOMBE) [4], where the advantages of both MOCVD and MBE can be utilized. For this paper, we will discuss preliminary studies of the growth of InN, GaN and AIN by this technique. In addition, we will discuss the potential for use of InN as an aide to formation of ohmic contact [7], as this is associated along with advanced processing procedures like dry etching [8,9], to the development of a nitride based device technology.
EXPERIMENTAL
Samples were grown in an Intevac Gas Source Gen II on 2" diameter semi-insulating GaAs and Al 2 03 sapphire substrates. Growth temperatures were monitored with the substrte thermocouple. Prior to deposition of the nitride films on the GaAs substrates, 3000A GaAs buffer layers were grown using triethylgallium (TEG) and AsH 3 , which was decomposed in a low pressure cracker at 1100°C. Since sapphire is transparent, a GaAs backing wafer was used to absorb the radiation from the substrate heater. Trimethylindium (TMI), trimethylamine alane (TMAA) and TEG were used as the In, Al and Ga srurce:, Mat. Res. Soc. Symp. Proc. Vol. 282. 01993 Materials Research Society
600
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