| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 90 === InP-Based microwave devices have many advantages over GaAs-Based microwave devices, including the lack of aluminum, less surface recombination velocity(~103 cm/sec), small bandgap of InGaAs, high thermal conductivity of InP substrate (0.7 W-cm/K) and suitable for 1.3 and 1.55 μm optoelectronics application. However, the InP substrate has the disadvantages of higher cost, the lack of large wafer and frailness let the usage of the commercial application has more difficulty. For these season, we investigate a new method to directly grow the metamorphic structure by low pressure metalorganic chemical vapor deposition (LP-MOCVD).
In the LP-MOCVD system, it is necessary to grow epitaxial layers at higher temperature and with higher growth rates compared with MBE, which will give rise to rougher surfaces of the metamorphic buffer layers grown on GaAs substrates. Because of the LP-MOCVD system is a more practice growth tool for obtaining thick epitaxial layers, growth was carried out in a commercial LP-MOCVD system with an AIXTRON 2400 planetary (vertical) reactor.
In this work, we overcome the drawback of surface roughness of metamorphic buffer layer in the case of the LP-MOCVD technique and have grown metamorphic buffer layers with various thickness on misoriented GaAs (1 0 0) substrates by 10 degree towards (1 1 1) A. The grown films are characterized by optical microscopy, atomic force microscopy, secondary ion mass spectrometry, transmission electron microscopy and double-crystal X-ray diffraction investigation. We also analyze the surface morphology, which is dependent on growth temperature, group III and group V partial pressure, growth rate and V/III ratios. Finally, a mirror like, uniform surface and high crystal quality of the metamorphic buffer layer directly grown on a GaAs substrate can be achieved.
In order to compare the performance between the metamorphic microwave devices and lattice-matched microwave devices in the future, we also fabricate the InAlAs/InGaAs modulation-doped field effect transistors on InP substrates. We measure and analyze the data of the InAlAs/InGaAs HEMTs, so that in the future work it will be compared with the data of the metamorphic HEMTs.
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