Structure and properties of GaNxOy films grown by nitridation of GaAs (1 0 0) substrates

doi:10.1016/j.jcrysgro.2003.11.022

Journal of Crystal Growth

Volume 261, Issues 2–3, 19 January 2004, Pages 324-329

https://doi.org/10.1016/j.jcrysgro.2003.11.022 Get rights and content

Abstract

GaAs (1 0 0) substrates have been heat-treated in a metal-organic chemical vapor deposition reactor under flows of NH₃ and an oxygen organo-metallic precursor at temperatures between 650°C and 750°C. Yellowish films formed at the surface of all the samples. Gallium, nitrogen and oxygen were detected by EDX analysis of the films. The oxygen content was estimated in the range of at 5–10 at% depending on the heat-treatment temperature. X-ray diffraction and HRTEM results indicate that the structure of the films corresponds to the hexagonal wurtzite phase of GaN with an expanded unit cell. Raman spectra show bands corresponding to the Raman active GaN modes as well as disorder-activated broad bands below $450 cm^{−1}$ related to the oxygen content in the films.

Introduction

Gallium nitride and related nitride semiconductors are widely used as promising materials for applications such as blue light emitters [1] and high-power high-frequency electronic devices [2]. Vapor-phase epitaxial growth techniques, such as metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), are usually used to obtain hexagonal wurtzite GaN films on sapphire substrates [3]. More recently, it has also been reported that cubic zincblende GaN films can be grown by vapor-phase epitaxy on some other substrates with cubic structure, such as GaAs [4] and Si [5]. Moreover, it has been demonstrated that GaN and related compounds could be obtained by nitridation of GaAs (1 0 0) substrates [6], [7], [8]. On the other hand, oxygen is a common substitutional impurity in GaN crystals. The maximum solubility of oxygen in the wurtzite GaN structure is, according to Pankove [9], about 30 at%. High concentrations of oxygen can affect the optical and the thermal properties of GaN [10]. Studies concerning the oxidation of GaN surfaces or the passivation of GaAs surfaces have addressed the growth and the analysis of gallium oxynitride thin films [11].

In this work, we report the properties of GaN_xO_y films obtained by the surface reaction of GaAs (1 0 0) substrates with ammonia gas in a CVD reactor in the presence of an oxygen organo-metallic (OM) precursor. The reaction temperature was varied in the 600–750°C range. Different experimental techniques such as X-ray diffraction, Raman spectroscopy, EDX, SEM and HRTEM were used to analyze the composition and the structure of the films as a function of the heat-treatment conditions.

Section snippets

Experimental procedure

The (1 0 0) GaAs substrates were heat-treated in a MOCVD system yet described [12]. The process was carried out under flows of NH₃, titanium isopropoxide (TiP) OM precursor and N₂ which was used as carrier gas. Typical flow rates were: 0.5 slm of N₂ through the TiP held at 40°C, 0.5 slm of NH₃ and 1 slm of N₂ total carrier gas flow rate. Previous works have shown that TiP is a titanium and oxygen precursor for the MOCVD growth of TiO₂ [13] and TiN_xO_y [12] films. Prior to their introduction in the

Results and discussion

Yellowish films are formed on the surface of all the heat-treated samples. These films show wrinkles probably as a consequence of stress due to the difference of lattice constant and thermal expansion coefficient between the film and the substrate, as previously described by Shimaoka et al. [6] for GaAs nitridation under NH₃ only. The films peeled off from the GaAs surface tend to roll up. Nomarski interference optical microscopy observation of these films (Fig. 1) shows blue-colored fringes

Conclusions

In summary, GaN_xO_y thin films have been formed at the surface of GaAs (1 0 0) substrates by a nitridation process under flows of NH₃ and an oxygen OM precursor at temperatures between 650°C and 750°C. X-ray diffraction and HRTEM results indicate that the structure of the films corresponds to the hexagonal wurtzite phase of GaN with an expansion of the lattice unit cell of about 4%. This lattice expansion is due to the oxygen content in the films which is estimated to be around 5–10 at% depending

Acknowledgements

The authors are grateful to P. Vennegues and P. Gibart from CRHEA-Sophia-Antipolis for the use of TEM facilities and for providing the epitaxial GaN layer used for comparison, respectively. The authors acknowledge M. Schowalter from LEM-Karlsruhe for the use of the DALI software.

References (19)

E. Kim et al.
J. Crystal Growth
(2002)
S. Nishimura et al.
Appl. Surf. Sci.
(2000)
G. Shimaoka et al.
Appl. Surf. Sci.
(1999)
G. Shimaoka et al.
Appl. Surf. Sci.
(2001)
Y. Ould-Metidji et al.
Appl. Surf. Sci.
(2003)
G.A. Slack et al.
J. Crystal Growth
(2002)
V.Y. Davydov et al.
J. Crystal Growth
(1998)
S. Nakamura et al.
Appl. Phys. Lett.
(1998)
R. Li et al.
IEEE Electron. Dev. Lett.
(1999)

There are more references available in the full text version of this article.

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Citation Excerpt :
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Structure and properties of GaNxOy films grown by nitridation of GaAs (1 0 0) substrates

Abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusions

Acknowledgements

J. Crystal Growth

Appl. Surf. Sci.

Appl. Surf. Sci.

Appl. Surf. Sci.

Appl. Surf. Sci.

J. Crystal Growth

J. Crystal Growth

Appl. Phys. Lett.

IEEE Electron. Dev. Lett.

Structure and properties of GaN_xO_y films grown by nitridation of GaAs (1 0 0) substrates