GaN x As 1-x Growth by Molecular Beam Epitaxy with Dispersive Nitrogen
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GaNXAs1-X Growth by Molecular Beam Epitaxy with Dispersive Nitrogen S.Z.Wang(a)(b), S.F.Yoon(a), T.K.Ng(a), W.K.Loke(a), and W.J.Fan(a) (a) School of Electrical and Electronic Engineering, Microelectronics Center, Block S1, S1-B2c-20, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Republic of Singapore (b) Singapore-Massachusetts Institute of Technology(MIT) Alliance, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Republic of Singapore E-mail: [email protected]; [email protected] Abstract The effect of energetic nitrogen ion bombardment during growth may have a deleterious effect on the material quality. To avoid the bombardment effect of energetic nitrogen ions, a modified mode for GaAsN growth using dispersive nitrogen is reported. High quality GaAsN epilayers and good GaAsN/GaAs interface were achieved using this growth mode. The results suggest that the surface of samples grown using dispersive nitrogen has fewer defects than those grown using direct nitrogen beam. The optical property of GaAsN samples grown using the dispersive nitrogen technique was found to improve, due to the lower ion bombardment effect. This growth technique is expected to be advantageous for growing high quality GaAsN materials for optoelectronic applications. I. Introduction The increasing demand for 1.3µm and 1.55µm optical communication systems and networks paves the way for the development of new material systems such as GaAsbased nitrides. This material system offers the serious possibility of making devices that are able to operate at such wavelengths due to the large bandgap bowing effect. Laser diodes operating at 1.3µm wavelength based on the quarternary GaInAsN on GaAs substrate have been demonstrated[1]. The use of GaAs-based GaInAsN and GaAsSbN materials for potential applications in 1.55µm laser diode application has also been reported[2]. The high conduction band discontinuity of possibly more than 300meV at the interface of the III-(V,N)/III-V heterostructure[3] has the potential of creating semiconductor lasers with high characteristic temperature (To) exceeding 150K. Indeed recently, a T0 value of 148K was demonstrated in GaInAsN/GaAs quantum well lasers emitting at 1.3µm[4]. Recent attempts have been focused on obtaining GaAs-based nitrides of sufficiently high quality for the fabrication of laser diodes. A number of epitaxial techniques have been reportedly used for growing GaAsN. These include metalorganic chemical vapor deposition (MOCVD)[5], molecular beam epitaxy (MBE)[6] and metalorganic molecular beam epitaxy (MOMBE)[7]. It is often known that most nitrides are relatively stable at the growth temperatures used in MOCVD due to the strong N-X bonds, hence making it difficult to incorporate nitrogen atoms into GaAs. Using the plasma-assisted molecular I3.1.1
beam epitaxy (MBE) technique, a large nitrogen concentration in excess of 10%[8] has been successfully incorporated into the GaAsN materials. However, the layer quality could be susceptible to damage due to the presenc
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