Paper EM-ThP13
The Influence of Ammonia - MO Precursors Pulse Separation on the Gallium Incorporation in Indium-Rich In_xGa_1-xN Epilayers

Thursday, November 3, 2011, 6:00 pm, Room East Exhibit Hall

Ternary In_xGa_1-xN alloys and embedded epilayers are of great interest due to their large band gap tenability, which enables new applications in the fields of advanced optoelectronic devices. Here, the growth of ternary In_xGa_1-xN epilayers is explored by high-pressure chemical vapor deposition (HPCVD) and pulsed precursor injection in order to reduce the temperature gap between the binary alloys GaN and InN and to improve the phase stability on the ternary alloys. In the pulsed precursor injection approach, the precursor separation times between the metal organic (MO) sources (TMI and TMG) and ammonia (S₁), and ammonia and MO (S₂) are two critical process parameters. Previous studies on InN growth showed that the precursors separation critically influences the surface chemistry and the resulting structural and physical layer properties.

In this contribution, we present results on indium-rich InGaN epilayers grown by simultaneous MO injection and with different S₂ timings, with the aim to find the optimum S₂ separation for high quality, single-phase InGaN epilayers. We will show that the S₂ separation is critical for the incorporation of gallium into the epilayers. In order to maintain single-phase epilayers, the S₂ separation has to be increased from S₂=400 ms for InN to over 1200 ms for In_xGa_1-xN with x=0.2. Raman spectroscopy and X-ray diffraction (XRD) are used to study the structural properties and the Fourier Transform Infra-red (FTIR) and transmission spectroscopy are used to study the electrical and optical properties of the epilayers.