Low Interface State Density at Pseudomorphic ZnSe/Epitaxial GaAs Interface
- PDF / 405,447 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 7 Downloads / 215 Views
LOW INTERFACE STATE DENSITY at PSEUDOMORPHIC ZnSe/EPITAXIAL GaAs INTERFACE
Q.-D.Qian, J.Qiu, M.Kobayashi, R.L.Gunshor, L.A.Kolodziejski*, M.R.Melloch, J.A.Cooper,Jr, J.M.Gonsalves, and N.Otsuka Purdue University, West Lafayette, Indiana, 47907 USA, *Permanent address: Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA. ABSTRACT The electrical properties of pseudomorphic ZnSe/epilayer GaAs heterointerfaces, grown by MBE, have been investigated by capacitance versus voltage (C-V) and current versus voltage (IV) measurements. Hole accumulation and inversion were observed in ZnSe/p-GaAs interfaces and ZnSe/n-GaAs interfaces, respectively. The C-V characteristics of the Au/ZnSe/p-GaAs capacitors are nearly ideal, exhibiting an interface state density (2.5xl011cm- 2 ) which compares favorably with the densities reported at AlGaAs/GaAs interfaces. INTRODUCTION An unpassivated GaAs surface possesses a large surface recombination velocity which limits the device performance. Proper passivation of the GaAs surface is an increasingly important subject. Despite numerous efforts, surface passivation of GaAs using deposited insulator or native oxide has not yet yielded satisfactory results [1] . An alternative way of passivating the GaAs surface is to grow an epitaxial layer of a high quality semiconductor to preserve the interface. ZnSe possesses a close lattice constant to GaAs, and they have highly compatible thermal expansion coefficients. The wider bandgap of ZnSe (2.67eV at room temperature), compared to that of AlGaAs (2.0eV for an Al mole fraction of 0.5), suggests a variety of device applications where ZnSe may present as alternative to AlGaAs for passivation of GaAs. Photoluminescence [2,3], transmission electron microscopy (TEM) [2-4], and piezomodulated reflectance spectroscopy [5] indicate high quality pseudomorphic ZnSe is grown by MBE onto epitaxial layers of GaAs (2,3]. An epitaxial ZnSe/GaAs heterojunction has recently been employed in a field effect transistor structure [4] where pseudomorphic ZnSe forms a pseudo-insulator on epitaxial layers of GaAs. In this paper, we discuss the electrical characterization of the pseudomorphic ZnSe/epitaxial GaAs heterojunction consisting of capacitance-voltage (C-V) and current-voltage (I-V) measurements. Both p- and n-type GaAs epitaxial layers are investigated. MBE GROWTH AND DEVICE FABRICATION The heterostructures used in this study were grown by two different growth procedures. The first growth procedure consisted of growing ZnSe and GaAs layers in two separate Perkin-Elmer 400 model MBE systems. The growth was performed on (100) p+ (n+) GaAs substrates. The Be (Si) doped 1.5 to 2.09m thick GaAs layers were grown at 600 0 C. To stimulate an as-grown surface for subsequent nucleation of ZnSe, the completed GaAs epilayer was passivated with amorphous arsenic [4]. The GaAs Mat. Res. Soc. Symp. Proc. Vol. 145. ©1989 Materials Research Society
424
10
12 10 KHz:
8
1MHz 0.2 0.3 0.4
6 4 1 MHz
1.0 1.5
2
.2
0
2
4
E.
z2MHz
6
wJ wU
annealed
Data Loading...
