Molecular Beam Epitaxy of Group-III Nitrides on Silicon Substrates: Growth, Properties and Device Applications

Abstract

We report on the growth and properties of GaN films grown on Si(111) substrates by molecular beam epitaxy using ammonia. The properties of the layers show that our growth procedure is very efficient in order to overcome the difficulties encountered during the growth of nitrides on silicon substrates: first, no nitridation of the silicon substrate is observed at the interface between the AlN buffer layer and the silicon surface; second, there is no Si autodoping coming from the substrate and resistive undoped GaN layers are obtained; and, also, strain balance engineering allows one to grow thick GaN epilayers (up to 3 mm) without formation of cracks. The optical, structural and electrical properties of these films are studied. In order to evaluate the potentialities of III-V nitrides grown on silicon substrates, we have grown heterostructures to realize light emitting diodes (LEDs), photodetectors and high electron mobility transistors (HEMTs).Introduction GaN-based devices have demonstrated a large potential for applications in electronics and optoelectronics [1]. For all these applications, the III-V nitride layers are usually grown on sapphire or silicon carbide substrates. However the development of some of these applications on silicon substrates has obvious technological advantages. This is the reason why significant research efforts have been made recently in this direction as shown by the wide variety of techniques which have been assessed. Indeed, techniques including conventional growth by MBE [2][3][4] or MOCVD [5-9] using various buffer layers, combination of MBE and MOCVD [10], growth on patterned substrates [11,12], selective area epitaxy [13,14], conventional ELOG [15,16], mask-less ELOG [17], pendeo-epitaxy [18], wafer bonding and film lift-off [19,20] etc. have all been already used in order to find a successful process for the growth and/or the realization of GaN-based devices on silicon substrates.With a such successful process it is expected that high-quality single crystalline GaN layers on silicon will be obtained despite the large lattice mismatch between GaN and Si. However, to achieve this goal, some other difficulties encountered during the growth of nitride on silicon substrates have also to be solved. Up to now as demonstrated for the first time by Watanabe and co-workers [21], the use of high temperature AlN buffer layers seems to be the best candidate for the heteroepitaxial growth of GaN on silicon substrates. The formation of the AlN/Si interface is already a critical issue because aluminum can diffuse in the silicon substrate and form a p-type inversion layer [22,23] in the substrate. Moreover the presence of reactive nitrogen species at the

GaN HEMT and MOS monolithic integration on silicon substrates

“…Currently, the applications for AlGaN/GaN HEMT devices are limited to RF and microwave power transistors, as well as some preliminary power switching applications, due to the restrictive cost of growth compared to silicon-based alternatives. The development of growth on silicon substrates allows for a cheaper alternative than the current norm of silicon carbide substrates [2,3].…”

“…Currently, the applications for AlGaN/GaN HEMT devices are limited to RF and microwave power transistors, as well as some preliminary power switching applications, due to the restrictive cost of growth compared to silicon-based alternatives. The development of growth on silicon substrates allows for a cheaper alternative than the current norm of silicon carbide substrates [2,3].The growth of AlGaN/GaN on Si also opens the path to the integration of high-density, low-power MOS logic with high power HEMTs, expanding the number of applications for which GaN can be competitive. Applications that can take advantage of this could include highpower switching circuits that use MOS logic for control, or chemical/biological sensors which can take advantage the chemical inertness of the AlGaN/GaN material structure for detection, combined with low-power MOS read-out circuitry.…”

“…The layer stack, which is shown in Fig. 1, uses the stress relief strategy developed in [2] in order to overcome the lattice and thermal expansion mismatch between GaN and silicon. It should be noted that the sample used in this work has an unintentionally doped buffer layer rather than using carbon doping.…”

Low loss GaN waveguides for visible light on Si substrates

“…From the optical point of view Si is not a desired material since it absorbs in the visible and the UV. Early developments of the epitaxy (both MBE and MOCVD) of GaN on Si [4,5] have allowed to solve most problems, so that many devices have been fabricated based on GaN grown on Si [6]- [10]. SHG based on modal phase matching was obtained in GaN and AlN microrings on Si substrate covered by SiO 2 insulator [11,12].…”

Growth of nitride‐based light emitting diodes with a high‐reflectivity distributed Bragg reflector on mesa‐patterned silicon substrate

“…The first nucleation steps on the Si substrate are described in Ref. [8]. The buffer layer is an AlN layer which is also the first layer of the DBR.…”