Patrick P.-T. Chen

Nitrogen-rich indium nitride

K.S.A.B. would like to acknowledge the support of an Australian Research Council Fellowship. We would also like to acknowledge the support of the Australian Research Council through a Large grant and a Discovery grant; the support of a Macquarie University Research Development Grant, and the Australian Institute of Nuclear Science and Engineering for SIMS access.

The nature of nitrogen related point defects in common forms of InN

The role of point defects related to the presence of excess nitrogen is elucidated for InN thin films grown by different techniques. Elastic recoil detection analysis has shown the presence of excess nitrogen in state-of-the-art InN films. Using x-ray photoelectron spectroscopy and x-ray diffraction it is shown that two distinct forms of point defects can be distinguished; one of these appears to be an interstitial form of nitrogen, common in some forms of polycrystalline InN. The other is associated with a combined biaxial and hydrostatic strain observed for molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) grown films, and may be a mixture of the nitrogen-on-metal antisite defect and lower densities of indium vacancies and interstitial nitrogen. The high density of defects present in all the InN samples examined suggests that stoichiometry related point defects dominate the electrical and optical properties of the material. The difference in the type of point defect observed for polycryst...

Crystal size and oxygen segregation for polycrystalline GaN

The authors would like to acknowledge the support of a U. S. NICOP Contract, No. N00014-99-1-GO17 sponsored through the U. S. Office of Naval Research. One of the authors (K.S.A.B.) would like to further acknowledge the support of a Macquarie University Research Fellowship.

Recrystallization prospects for freestanding low-temperature GaN grown using ZnO buffer layers

Remote plasma enhanced-laser-induced chemical vapor deposition was used to grow gallium nitride films on zinc oxide buffer layers deposited by atomic layer epitaxy on soda lime glass. Freestanding layers of gallium nitride were processed by etching away the substrate and ZnO buffer layer. The n-type carrier mobility for the GaN on ZnO/soda lime glass was found to be similar to the highest values achieved on pure silica, and was accompanied by high carrier concentration. As-grown polycrystalline materials were recrystallized at low temperature (below the 570°C gallium nitride growth temperature). This recrystallization process greatly improved the film structure with a self-assembled multilayer structure evident in the oxygen-rich surface layer of the films that had undergone the process.

Low activation energy for the removal of excess nitrogen in nitrogen rich indium nitride

For some InN films large amounts of excess nitrogen are seen at low growth temperatures. Recent studies have revised downward the defect formation energies for several forms of nitrogen rich point-defects in InN. Here we calculate an activation energy of 0.4 ± 0.1 eV for the thermally activated removal of much of the excess nitrogen, believed to be interstitial nitrogen. This low energy barrier is shown to support the case for a low defect formation energy of the same native defect, although it is pointed out that non-equilibrium plasma based conditions are required to reach these lower defect formation energies.

Glass substrates for GaN using ZnO buffer layers

Polycrystalline GaN has been grown by remote plasma enhanced laser induced chemical vapour deposition on soda lime glass substrates using ZnO buffer layers. The high compliance of the ZnO has allowed relatively thick layers of 5-10 microns to be produced on these inexpensive substrate materials. These were subsequently processed into free standing layers. Hall mobilities have been measured for n-type GaN deposited on the ZnO buffered glass substrates, with the results equaling the highest values obtained by others using MBE and high purity silica substrates.

UV Moderation of Nitride Films during Remote Plasma Enhanced Chemical Vapour Deposition

GaN and AlN thin films have been grown by remote plasma enhanced chemical vapour deposition (RPE-CVD) with the assistance of ultraviolet (UV) irradiation during growth. High quality AlN insulating layers have been grown at room temperature for MIS devices. Film resistivities of up to 2.8 × 10 16 Ωcm and breakdown fields of over 1.8 MV/cm have been achieved. Preliminary results for GaN indicate severe nitrogen loss when using UV desorption with an ammonia plasma, however no nitrogen deficit is seen when using a nitrogen plasma. Optical absorption data show substantial improvement in material quality when using a nitrogen plasma in preference to an ammonia plasma for GaN RPE-CVD growth.

Properties of InN Grown by Remote Plasma Enhanced Chemical Vapour Deposition

We have investigated the properties of indium nitride (InN) grown at various temperatures on c-plane sapphire substrates using remote plasma enhanced chemical vapour deposition (RPECVD). The optical absorption spectra show a broad range of the apparent band-gap from 0.90 to 2.18 eV, depending on the growth temperature. These two extreme apparent band-gaps are similar to the controversial values of 0.7 and 1.9 eV quoted in the InN band-gap debate. Along with optical absorption results, the influence of growth temperature on growth rate, and carrier concentration is discussed. The correlations between the carrier concentration, and shallow-donors (oxygen and hydrogen) in InN are also analysed

Growth and characterisation of GaN grown by microwave plasma assisted laser-induced chemical vapour deposition

Growth of microcrystalline GaN films by microwave plasma assisted laser-induced chemical vapour deposition has been studied in the temperature range of 525/spl deg/C - 650/spl deg/C for growth on sapphire and silicon. The influence of substrate temperature is discussed and growth mechanisms are explained. Properties of the GaN films are measured by X-ray diffraction and optical transmission spectroscopy.