LabVIEW automatic control program design for the home-made metalorganic chemical vapor deposition(MOCVD) system and study on the optical and electrical properties of low-temperature grown gallium nitride(LT-GaN)
| Autor: | Wong, Chia-Jiun, 翁嘉駿 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 This thesis is divided into two major parts. One is focused on automatic control epitaxy program design for the home-made MOCVD system based on LabVIEW platform. The other one is focus on the study on the optical and electrical properties of low-temperature grown gallium nitride(GaN). The main function of LabVIEW control program is to integrate all the apparatus installed on the home-made MOCVD system, and its most featured function is that data flows can be transmitted and received simultaneously within 0.1sec by using "#8 independent RS-232 ports" parallel protocol flow-bus microprocessor cards. The LabVIEW epitaxial control program also have embedded sub-trigger routine program that designed for continuing detecting the various default emergency states, if any of the emergency state triggers, the LabVIEW program will automatically forced itself to load into the user-defined safety state mode to make the first aid of crews and system. The WK2008 MOCVD epitaxy program had been executed over 185 runs, well proving its stability and reliability. The epitaxy control program on LabVIEW platform is comparable to commercial MOCVD system in various aspects. The second part of this thesis is study on the optical and electrical properties of low-temperature grown gallium nitride(LT-GaN) by our home-made MOCVD. We use our home-made MOCVD called WK2008 TP-MOCVD system to grow a series of Low-temperature GaN ranging from 650 to 1130°C. And we use 13K PL measurement to characterize the epitaxial quality of LT-grown GaN films. According to our data, we show the lowest temperature grown GaN at 700°C that the 13K PL spectrum is dominated by near-band edge emission (NBE, 3.47eV) without defects or impurities related yellow band luminescence (YL, 2.2eV). To our knowledge, no GaN film with this dominant NBE within temperature range that less than 900°C have been grown before by any technique using NH3 as V source. Besides, in our 13K PL data, an anomalous behavior of NBE peak intensity and integral intensity of full spectrum had been observed. In the medium temperature range (800-850°C), the NBE peak intensity and integral intensity of full spectrum is greatly reduced, and the exact reason for this phenomenon is still unclear. We may possibly attribute it to relating to the concentration of (N-H)x radicals that is produced by NH3 thermal cracking. The 13K PL main emission peak of 650°C grown GaN is "red-shifted" to 3.27eV. The postulation of cubic/hexagonal mixed phases in 650°C grown GaN is preliminary precluded by the single diffraction peak (34.52°) of θ/2θ XRD experiment. The possible reason of red-shift may be attributed to the dominance of donor acceptor pair (DAP) and its 1st and 2nd phonon replicas of hexagonal phase GaN, because of its approximately equallivant energy separation (about 70-90meV) between the sequential emission peaks. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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