Growth of AlGaAs/GaAs Modfet Structures by Gsmbe Using Triethylalkyls and Arsine
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GROWTH OF AIGaAs/GaAs MODFET STRUCTURES BY GSMBE USING TRIETHYLALKYLS AND ARSINE Yu-Min Houng*, Yi-Ching Pao *, and Paul McLeodl *Hewlett-Packard Labs, Palo Alto, CA 94304 #III-V Device Center, Varian Associates, Santa Clara, CA 95054 §MBE Equipment Operation, Varian Associates, Santa Clara, CA 95054
ABSTRACT We have grown high quality AlGaAs/GaAs heterostructures by GSMBE, using triethylalkyls and arsine, for MODFET device applications. Al1.Ga.As/GaAs modulation-doped structures with moblilities as high as 7,200 and 47,000 cm 2/V-s at 300 and 77K, respectively, were obtained for a spacer layer thickness of 30A and a sheet carrier concentration of lxl012 cm- 2. These results are comparable to films of a similar structure grown by elemental source MBE or by OMVPE techniques. Quarter-micron gate length MODFETs fabricated from this material have fr greater than 38 GHz and exhibit a 1.7 dB noise figure with 10 dB associated gain at 18 GHz when operated at room temperature.
INTRODUCTION Gas Source Molecular Beam Epitaxy (GSMBE) using gas sources for both group III and V elements has attracted increasing interest in recent years because of the possibility of combining the advantages of Organo-Metallic Vapor Phase Epitaxy (OMVPE) and Molecular Beam Epitaxy (MBE). GSMBE offers several potential advantages such as excellent uniformity of the epitaxial layer, excellent surface morphology with very low defect density and excellent control of alloy composition in the phosphorus containing compounds. This technique has been used to prepare high quality GaxInixAsyPiy photonic and electronic devices with state-of-the-art performance [1-61. However, the growth of high quality AlGa 1_.As/GaAs heterostructures for high-speed device applications, such as Modulationdoped FET (MODFET), has not been demonstrated. The main reason for this is that the materials produced by this technique have a relatively high concentration of carbon which degrades electronic transport properties in these materials, especially in the AlGaAs films. In this paper we report the GSMBE growth of AlxGa1 _,As and GaAs with reduced carbon incorporation and MODFET devices fabricated from this material with performance comparable to that of devices fabricated from materials produced by conventional, elemental source, MBE.
EXPERIMENTAL The epitaxial layers used in the present study were grown in a Gas Source MBE system. Mat. Res. Soc. Symp. Proc. Vol. 145. @1989 Materials Research Society
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This system is based on a modified Modular Gen II MBE chamber with a 1500 1/s turbomolecular pump and a cryopump which maintain the growth chamber at a pressure of less than 5x10 5 torr during growth. The typical total gas flow rate during growth is less than 30 sccm. To ensure precision control and stability, the gas manifold incorporates an electronic mass flow controller to regulate the group V hydride (AsH 3) gas flow, and a combination of electronic mass flow controllers, for hydrogen carrier gas flow control, and a closed-loop pressure controller, for controlling gro
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