The Optical Properties of Isoelectronic Indium doped P-type GaN films

• Main Authors: Wei-Hao Lee, 李偉豪
• Other Authors: Ming-Chih Lee
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/90108121879534734062

碩士 === 國立交通大學 === 電子物理系 === 89 === The optical properties and metastable behavior of Mg-In codoped GaN thin films (grown on sapphire) were characterized by photoluminescence (PL), photoluminescence excitation (PLE), Raman spectra and X-ray diffraction. The PL spectra of as-grown Mg-In codoped GaN show two emission peaks around 2.88eV and 3.18eV with oscillations due to the microcavity interference effect. For the sample doped with Mg only (CP2Mg=250sccm), the 2.88eV band dominates the PL spectrum. For the sample codoped with Mg and In (CP2Mg:250sccm+TMIn:100sccm), the PL spectrum begins to show the 3.18eV band. When the TMIn flow rate increases to 250 sccm, the 3.18eV band becomes the most intense. We also measured the excitation power dependence of PL spectra, in which the 2.88eV band can be attribuited to the Donor-Acceptor-Pair recombination (DAP) and the 3.18eV band is attribuited to the free to bound recombination (eA). These two transitions involve Mg-related acceptors, one is the deep Mg complex (dMg); the other is the common Mg acceptors (Mg0). The sample activation was treated by thermal annealing (TA) at 750 oC for 60 min. The Mg concentrations were determined to be from 2.69x1019cm-3 to 3.49x1019cm-3 by secondary ion mass spectrometry (SIMS) measurements. From the SIMS and the Hall measurements, the sample codoped with Mg and In (CP2Mg:250sccm+TMIn:250sccm) also exhibits the best activation efficiency. Furthermore, the FWHMs of the Raman spectra and XRC are the narrowest. The PL spectra show the similar trend as the Raman and XRC spectra. Besides, the special metastable behavior was observed in this sample. In order to understand the temporal behavior of two Mg-related emission bands, we carried out the measurements of PL intensity evolution. There are two categories by analyzing the distribution of decay time constants: one is for emissions from 380 nm to 400 nm having time constant on the order of ~ 1000 seconds; the other is for emissions from 410 nm to 460 nm with time constant on the order of ~ 100 seconds. For the sample doped with Mg only (CP2Mg=250sccm), the time constant for emissions from 380 nm to 400 nm is on the order of ~ 30 seconds; and that for emissions from 410 nm to 460 nm is on the order of ~ 100 seconds. Our results indicate that the density of state responsible for the 3.18eV emission band (Mg0) in GaN:(Mg+In) is more than that in GaN:Mg. In addition, we have also measured the PL intensity of GaN:(Mg+In) at 400 nm as a function of temperature and obtained an optical potential barrier between the common Mg acceptors (Mg0) and Mg related deep levels (dMg) to be about 103meV from the Arrehenius plot. It is greater than 69meV for GaN:Mg, and indicates that In could introduce larger potential barrier in GaN:Mg sample.