Influence of substrate polarity on growth of InN films by RF‐MBE

Abstract

We have investigated influence of substrate polarity on the growth of InN films by RF-MBE. It was found that the temperature required for successful growth of InN strongly depended on the substrate polarity. InN could be grown on C-face SiC at 550 °C, whereas no InN growth occurred on Si-face SiC at 550 °C. InN growth on Si-face SiC was realized at lower temperature of 450 °C. In the case of the growth on freestanding GaN substrates, InN could be grown on N-face GaN at 550 °C, whereas InN growth on Ga-face GaN was realized at 450 °C. It was found that InN with N polarity can be grown at higher temperature than that with In polarity. These results indicate that control of polarity is essential for successful growth of InN.1 Introduction InN is a very attractive material for future optical and electronic devices due to its excellent physical properties. However, the growth of high-quality InN is very difficult, because of the low dissociation temperature of InN and the extremely high equilibrium vapour pressure of nitrogen. Therefore, physical properties of InN and its growth mechanism are still not fully understood. In the case of GaN growth, the polarity of GaN is a key characteristic because the film with Ga polarity has better surface morphology and crystal quality than the film with N polarity [1]. It is also reported that the decomposition rate of GaN is dependent on the polarity [2]. Furthermore, for GaN-based electronic devices using piezoelectric effect, the strain and the polar direction of the film influence device performances [3]. Thus, to understand and control the effect of the polarity is essential and many efforts have been made on these issues for GaN-related materials [4][5][6]. However, the number of reports on polarity of InN is only a few [7,8] and it is not understood how the polarity of substrate influences the growth of InN. In this paper, we investigate the influence of substrate polarity on growth of InN films.

Thermal and chemical stabilities of In‐ and N‐polar InN surfaces

“…Thus there are two distinct {0001} planes along the c-axis: the (0001) N face (N-polarity) and the (0001) In face (In-polarity). We previously found that N-polar InN can be grown at temperatures approximately 100 °C higher than that for In-polar InN [4], consistent with Xu and Yoshikawa's result [5]. We also found that the polarities of InN films can be determined by either treating the films in KOH solution [6] or irradiating the films with atomic hydrogen (H*) [7].…”

“…We consider as follows. The dissociation of N atoms from the surfaces determines the thermal stability at these high temperatures, and N atoms can dissociate more easily from the In-polar surface than from the N-polar surface, as explained in our previous work [4]. …”

Crystal quality of InN thin films grown on ZnO substrate by radio-frequency molecular beam epitaxy

“…Matsuda et al have demonstrated that good crystal quality of InN can be achieved only on a N-face GaN substrate at high temperature. 9 In this study, we propose ZnO as a suitable substrate for InN growth. As already shown in Table I, ZnO also has a small lattice mismatch to InN.…”

“…Mainly two substrates, sapphire (Al 2 O 3 ) and GaN, are well used in recent research. 3,[8][9][10] Table I shows the lattice mismatch of each substrate for InN growth. Sapphire is most widely used; however, it has a very large lattice mismatch such that a low-temperature buffer layer is essential to remove the crystal stress.…”

Investigation of polarity dependent InN{0001} decomposition in N2 and H2 ambient

“…Wurtzite InN has two distinct planes along the c-axis: (0001) In-polarity and (000 1 ) N-polarity. To date, In-and N-polarity InN layers have been successfully grown using several methods such as molecular beam epitaxy (MBE) [4][5][6], metalorganic vapor phase epitaxy (MOVPE) [7,8], and hydride vapor phase epitaxy (HVPE) [9,10]. In addition, the polarity dependence of the thermal stability and decomposition reactions of InN layers in various ambients have been reported [11][12][13][14][15].…”