Time of Flight Mass Spectroscopy of Recoiled Ions Studies of Gallium Nitride Thin Film Deposition by Various Molecular B
- PDF / 162,776 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 182 Views
Internet Journal Nitride Semiconductor Research
Time of Flight Mass Spectroscopy of Recoiled Ions Studies of Gallium Nitride Thin Film Deposition by Various Molecular Beam Epitaxial Methods E. Kim1, I. Berichev1, A. Bensaoula1, A. Schultz2, K. Waters2 and W. Zagozdzon-Wosik3 1The
Space Vaccum Epitaxy Center, University of Houston,
2Ionwerks, 3Department
of Electrical and Computer Engineering, University of Houston,
(Received Tuesday, June 16, 1998; accepted Tuesday, September 15, 1998)
Gallium Nitride (GaN) thin films were successfully grown by electron cyclotron resonance molecular beam epitaxy (ECR-MBE), gas source MBE (GSMBE), and chemical beam epitaxy (CBE). Time of flight mass spectroscopy of recoiled ions (TOF-MSRI) and reflection high energy electron diffraction (RHEED) were used in-situ to determine the surface composition, crystalline structure, and growth mode of GaN thin films deposited by the three MBE methods. The substrate nitridation and the buffer layers were monitored and optimized by TOF-MSRI and RHEED. For GSMBE, the gallium to nitrogen ratio is found to correlate well with ex-situ optical properties. In the case of CBE, carbon incorporation determines the surface morphology, crystalline quality and optical activity of the epilayers.
1
Introduction
1.1 Time of Flight Mass Spectroscopy of Recoiled Ions
With many interesting and useful applications, GaN has become one of the most important optoelectronic materials. Among the GaN thin film growth methods, molecular beam epitaxy (MBE) growth has become a recognized technique for fabricating state-of-the-art short wavelength opto-electronic devices, although metal-organic chemical vapor deposition currently remains the technology of choice for producing the majority of GaN-based devices. [1], [2] Nevertheless, MBE is expected to be superior in terms of composition, thickness, doping, and interface control due to the beam nature of the source fluxes and the availability of various in-situ monitoring tools. In addition, the lower growth temperatures and the absence of residual impurities in the process should allow hetero-structures with controllable doping profiles, lower defect densities. Although GaN LED and laser diodes have been developed recently, the precise growth mechanism and the role of substrate nitridation and buffer layers are not yet clearly understood. Both substrate nitridation and buffer layer growth dramatically improve the quality of the GaN layers on the highly mismatched sapphire sub-
strate. [3], [4] It is generally accepted that the nitridation step provides a better template for GaN nucleation and the thin low temperature GaN or AlN buffer layers relax the interfacial stress. Ion scattering spectroscopy (ISS) is a well-established probe based on ion-solid interactions. A variant, called low energy ion scattering (LEIS) by time-of-flight (TOF) detection, is a powerful technique for surface structural and elemental analysis. [5] This technique has been proven as a real time thin film growth monitor in background pressur
Data Loading...
