| The Chemical Vapor Deposition Growth of Gallium Arsenide-Based Quantum Well ‘W' Structures for Mid-IR | ||
| Thomas F. Kuech1, Manish Rathi2, Anish A. Khandekar2, D.P. Xu3, J. Y. T. Huang3, J.H. Park3, Luke J. Mawst3, Xueyan Song4 and S.E. Babcock4, (1)Department of Chemical Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706, (2)Chemical nd Biological Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706, (3)Electrical and Computer Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706, (4)Materials Science and Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706
The conventional active region for achieving 1.55 μm wavelength operation is based on InGaAs- or InGaAsP-based multiple quantum wells (MQWs) on InP substrates. GaAs1-ySby-GaAs1-zNz type-II quantum well (QW) active regions hold potential for fabrication of 1.55 μm diode lasers on GaAs substrate. The lasing performance of InP-based vertical cavity surface emitting lasers (VCSELs) is inferior to that of GaAs-based VCSELs. Devices based on GaAs1-ySby-GaAs1-zNz should exhibit improved temperature insensitivity due to large band offsets between GaAs1-ySby and GaAs1-yNy. Strong overlap between electron-hole wavefunctions determines the differential gain of a lasing device. For mid-infrared range applications, the ‘W' structure is widely accepted, where a hole QW is sandwiched between two electron QWs that provides large wavefunction overlap. From k·p simulations, an antimony mole fraction of 0.35 to 0.4 in the GaAs1-ySby hole well layer and an nitrogen mole fraction of 0.01 to 0.015 in the GaAs1-yNy electron well layer are desired for strong carrier confinement and long emission wavelength. The broad miscibility gap between GaAs1-ySby and GaAs1-zNz prevents formation of a homogeneous alloy over the entire range of desired composition under conditions of thermodynamic equilibrium. Triethyl gallium, trimethyl antimony, dimethyl hydrazine and arsine are used as precursors in metal-organic vapor phase epitaxy (MOVPE) to grow GaAs1-ySby and GaAs1-zNz. As/III ratio in the gas phase affects the antimony incorporation in the solid film significantly. X-ray diffraction (XRD) as well as electron probe microanalysis (EPMA) techniques are used to determine the composition in the thin films. Abrupt interfaces between the thin layers of GaAs1-ySby and GaAs1-zNz are essential for device performance. Formation of an antimony segregation layer and possible arsenic-for-antimony exchange processes lead to interfacial grading and low antimony incorporation in thin layers. Gas switching sequences and optimization to achieve abrupt interfaces will be discussed. Samples were grown containing 3 ‘W' structured GaAs1-ySby - GaAs1-zNz layers, each separated by a GaAs layer and cladded by Al0.7Ga0.3As barriers on both ends. These samples were annealed under arsine at 650oC to remove probable nitrogen clustering. The photoluminescence (PL) results from these samples before and after annealing are compared. Annealing results in an increase in the intensity and a blue shift in the emission wavelength. The highest emission wavelength, 1457 nm, is achieved to date using a 3 nm GaAs0.6Sb0.4 and 2 nm GaAs0.988N0.012 ‘W' structure. Extended Abstract Status: Not Uploaded | ||