Deep Level Defect Characterization of MBE Grown Ingaas/Gaas Heterostructures
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DEEP LEVEL DEFECT CHARACTERIZATION OF MBE GROWN InGaAs/GaAs HETEROSTRUCTURES.
W.R.
BUCHWALDa,b,
J.H.
ZHAOb,
F.C.
RONGa
a)US Army Electronics Technology and Devices Lab., Fort Monmouth, NJ 07703 b)Dept. of Electrical and Computer Engineering,Rutgers University, Box 909, Piscataway, NJ 08855
ABSTRACT
Deep level transient spectroscopy (DLTS) measurements have been performed on Schottky diodes fabricated on MBE grown InGaAs/GaAs heterostructures. The dominant electron trap in this material is found at a depth of 0.30eV below the GaAs conduction band and is believed to be the previously observed M3 defect. Two other defects, at depths of 0.50eV and 0.58eV below the GaAs conduction band, were also observed. Defect depth profiling shows the 0.50eV defect to be spatially located near the heterointerface. The 0.58eV defect is not observed near the heterointerface but is observed in large concentrations deep in the GaAs epilayer. Optical DLTS measurements reveal deep defects at 0.54eV and 0.31eV above the InGaAs valence band as well as a large, broad peak, most likely consisting of several energy levels with varying capture cross sections, located at the heterointerface. Two carrier accumulation peaks were also seen in the CV carrier profiling measurements and are suggested to be due to two heterointerface defects located at 0.68eV and 0.87eV below the GaAs conduction band. Thermally stimulated capacitance measurements also indicate minority hole emission in this n-InGaAs/N-GaAs heterostructure.
Introduction
In recent years, much interest has been generated concerning the properties of heterostructures formed from semiconducting materials of differing band gaps. Devices such as tunnel diodes, double barrier heterostructure lasers, and high electron mobility transistors, rely on the quality of both the bulk material and the quality of the heterointerface to maintain peak device performance. In particular, the quantity, energy level, and spatial location of deep traps, are of prime importance due to the deep traps ability to act as a scattering mechanism, recombination center, compensation mechanism or tunneling site[l,2,3]. This work reports the electrical characterization of Schottky diodes fabricated on MBE grown In 0 . 0 8 3 Gao.9 1 7 As/GaAs heterostructures where the GaAs buffer and Ino 0. 8 3 Ga 0 . 9 1 7 As epilayer are 2jm and lpm respectively.
The Si doping flux was maintained constant to produce 3xl0 1 6 cm" 3 doping density in both the In 0 . 0 8 3 Ga0 . 9 1 7 As and GaAs2 layers. The area of the Schottky contact was measured to be 0.00413 cm . The Indium on the back of
the n+ substrate, present during the MBE growth, was used to make a back, ohmic,
contact.
Mat. Res. Soc. Symp. Proc. Vol. 209. @1991 Materials Research Society
698
Experiment
If uniform doping is assumed throughout both epilayers, then verticle CV[4] measurements made by biasing the top Schottky contact and the back n+ substrate reveal a number of anomalous features. These features consist of a zero bias capacitance value of about
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