Pd/Au:Be Ohmic Contacts to p-Type GaAs
- PDF / 1,206,496 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 27 Downloads / 215 Views
Pd/Au:Be OHMIC CONTACTS TO p-TYPE GaAs K.M. Schmitz, K.L Jiao, R. Sharma and WA. Anderson, Center for Electronic and Electro-optic Materials, Department of Electrical and Computer Engineering, State University of New York at Buffalo, Bonner Hall, Buffalo, NY 14260 G. Rajeswaran and L.R. Zheng, Corporate Research Laboratory, Eastman Kodak Company, Rochester, NY 14650 M.W Cole and R.T Lareau, U.S. Army Electronics Technology and Devices Laboratory, Fort Monmouth, NJ 07703 ABSTRACT Stable, low resistance ohmic contacts to p-type GaAs were studied for use in semiconductor laser applications. Comparison was made between Cr/Au, Au:Be and Pd/Au:Be metallizations. 0Regions of P + were formed in NGaAs by a spin-on source which was rapid diffused at 950 C for 6s. Surface doping of 2x10"/'/cm 3 and junction depth of 0.4 Ym were determined by SIMS, groove and stain, and electrochemical grofile. Metallizations were accomplished by thermal evaporation with a base pressure of 3x10 Torr. Sintering of the metallizations was done by furnace or RTA at 3500 C. This sintering temperature was selected after RBS studies predicted an absence of significant interdiffusion. Pd/Au:Be yielded the best result of 0.3 yQ-cm 2 based upon transmission line, cross-bridge Kelvin and van der Pauw studies. A layer of BeO was revealed on the surface of Au:Be contacts by Auger studies. Cross-section TEM studies on Pd/Au:Be revealed a uniform layer of alloyed Ga-Au with an absence of spiking. INTRODUCTION GaAs and its related compounds are becoming widely used in modern optoelectronic devices such as semiconductor lasers. Since high current density is utilized in laser operation, high quality ohmic contacts are required. These contacts must exhibit low resistance, thermal and electrical stability, and be compatible in fabrication with other processing steps. This research involves a GaAs/AlGaAs heterojunction laser with particular emphasis to an ohmic contact to the Zn-diffused p+ region. Alloyed ohmic contacts have been extensively studied and are the favored contact in present device technology [1]. Most ohmic contacts are based on a GaAs/X/Y/Z configuration. Here, X is a thin metal (eg: Pt, Ti, Cr, Pd) used primarily for adhesion purposes, and Y is an electrically conductive diffusion barrier layer consisting of a eutectic- type metal composition. Layer Z is a thick metal which is typically required for electrical contacts as well as to prevent oxidation of the metallization [2]. Some of the better ohmic contacts have utilized Ti/Pt/Au [3), Zn/Pd/Au [4] or Mn/Au [5]. This work explores the relationship between electrical and structural properties of Pd/Au:Be ohmic contacts to p-GaAs. DEVICE FABRICATION Substrates consisted of lxl cm 2 slices of (100) n-type GaAs, Si-doped to a carrier concentration of 5x1018cm"3. Wafers were capped with a 2500 A layer of Si 3N4 deposited by plasma chemical vapor deposition. Samples were patterned to form transmission line (TL), cross bridge Kelvin (CBK), lateral diffusion (LD) and step coverage (SC) patterns, all of w
Data Loading...
