Growth of wurtzite‐GaN on silicon (100) substrate by molecular beam epitaxy

Abstract

We report on the growth of wurtzite-GaN layers by molecular beam epitaxy using ammonia on Si(100) substrates. We show that using 4° misoriented Si(100) substrates, GaN layers are obtained with a dominant orientation. The nucleation conditions of the AlN buffer layer as well as the entire growth process are described and compared with the process developed for the growth on Si(111) substrates, already well optimised in our laboratory [1]. The crystalline quality and polarity are assessed by transmission electron microscopy, X-ray diffraction and chemical etching. The most noticeable features of the layers grown are the high crystal quality of the AlN/Si interface, the Ga-polarity of the final GaN layer and especially the presence of the wurtzite phase only.1 Introduction GaN-based devices such as Light Emitting Diodes (LED), High Electron Mobility Transistors (HEMTs) are usually grown on sapphire (Al 2 0 3 ) or silicon carbide (SiC) substrates. Nevertheless, the growth of device-quality GaN-based heterostructures on silicon substrates is of huge interest in terms of cost, availability, processing and integration. Hexagonal GaN has been already successfully deposited on Si(111) substrates either by metalorganic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE) methods, in spite of the difficulties related to the very high reactivity of the silicon surface with nitrogen, the large lattice mismatch (-16.2%) and the large difference in thermal expansion coefficient (113%). However, from the point of view of integrating GaN devices with silicon technology, the Si(100) substrate is preferred because it is the most widely used in silicon mainstream technology. Contrary to the (111) plane, the (100) silicon plane does not present a 6-fold symmetry but a 4-fold symmetry more suitable for the epitaxial growth of a cubic phase. Nevertheless, the (β-GaN) cubic phase is metastable, and the thermodynamically stable hexagonal GaN phase could be grown on the (100) plane. In addition to the square surface symmetry, the Si(100) nominal surface exhibits a 2x1 surface reconstruction with two types of domains rotated by 90°. Silicon atoms have dangling bonds which forms dimers in the [110] direction for one domain and in the [1][2][3][4][5][6][7][8][9][10] for the other domain. Adjacent domains are separated by a monoatomic step (a 0 /4) and have respectively 2x1 and 1x2 surface reconstruction. It has been shown that the presence of monoatomic steps leads to the formation of antiphase boundaries domains in GaAs grown on Si(100) (APBs)[2] and a two-domains structure rotated by 30° when growing 2H-AlN [3]. To obtain a silicon (100) surface with only one domain, single atomics steps must be annihilated or double atomics steps (a 0 /2) must be formed using, for example, a (100) vicinal plane [4]. Indeed,

Growth of single-domain GaN layers on Si(001) by metalorganic vapor-phase epitaxy

“…4). These results are roughly half the values recently published [16,18] indicating the achieved comparatively good quality of the GaN layers. For analyzing the selection process reciprocal space maps around the GaN(1 0 1 4) reflection were measured at different azimuth positions of 01 and 301 (Fig.…”

Blue light emitting diodes on Si(001) grown by MOVPE

“…This leads to the occurrence of two in-plane alignments of c-axis oriented crystallites, rotated by 30°, and thus, to the inhibition of coalescence of the GaN columns [4]. Recently, flat and mono-crystalline layers were obtained by using off-oriented substrates and high temperature AlN-based buffer structures grown by both metalorganic vapor phase epitaxy (MOVPE) [5,6], and molecular beam epitaxy [7,8]. Based on this approach, we investigate MOVPE grown InGaN/GaN-based light emitting diodes on Si(001) [9] by transmission electron microscopy (TEM), X-ray diffraction, and cathodoluminescence.…”

In situ HCl etching of Si for the elaboration of locally misorientated surfaces

“…A significant APD reduction occurs when using such substrates [10,11]. Long thermal anneals (from 1 h up to 12 h) at high temperatures (from 800 8C to more than 1000 8C) and under ultra high vacuum is one of the methods used for the fabrication of misorientated Si substrates with a regular array of steps on the surface [12][13][14][15].…”