Growth of InGaN Thin Films on Polycrystalline Metal‐Foil Substrates and Their Photoluminescence Properties

Abstract

PACS : 68.55.Ac; 78.66.Fd Polycrystalline metal foils are candidates as large area, flexible, lightweight and inexpensive substrates for nitride thin-film growth. Attempts have been made to grow InGaN thin films, in addition to GaN thin films, on such polycrystalline high-melting-point metal foils, and the photoluminescence properties of the prepared films are investigated. The band edge emission is observed for the prepared InGaN thin film although the film is grown on a polycrystalline Ti metal foil, and the emission intensity is enhanced compared to that of a GaN thin film grown on the same substrate. The UV emission becomes much stronger when the InGaN thin film is grown after deposition of an amorphous SiO 2 intermediate layer on the Ti foil substrate.Introduction Several kinds of highly efficient discrete devices such as light-emitting diodes (LEDs) and laser diodes (LDs) using GaN thin films have been developed. Generally in fabrications of GaN discrete devices, single-crystal substrates are used to grow single-crystal GaN thin films. However, single-crystal substrates such as sapphire are expensive and their substrate areas are limited to a small size. However, polycrystalline metal foils can be used as large area, flexible, lightweight and inexpensive substrates for application of GaN thin films to emissive giant microelectronic devices [1], if the required electrical and optical properties can be obtained when GaN thin films are grown on these substrates. Since adequate growth temperatures of GaN thin films are quite high, plastic substrates cannot be used for the growth. This problem can be easily solved by the adhesion of metal foils onto the plastic substrates after the growth of GaN thin films. Nakamura et al.[2] reported that the deep-level emission of GaN was very strong while the band edge emission was weak in photoluminescence spectra of GaN epitaxial films grown on sapphire substrates by the two-flow metal organic chemical vapor deposition method, although the crystal quality of the GaN epitaxial film was quite high. Conversely, the band edge emission became intense when InGaN epitaxial films were grown by the same growth system, and the deep-level emission became weak [3]. There have been many reports on such superior luminescence properties in InGaN thin films. InGaN alloys show intense luminescence due to the exiton localization because of the large compositional fluctuations [4,5]. It is not certain that the enhancement mechanism can be applied to polycrystalline systems; we attempted to grow InGaN thin films on polycrystalline metal foil substrates and the photoluminescence properties of the prepared films were investigated.

Some Properties of Group-III Nitride Thin Films Directly Grown on Non-Single-Crystalline Substrates by Using a Molecular Beam Epitaxy Apparatus

“…Nitride semiconductor thin films often become poor polycrystalline when they are grown on polycrystalline substrates because of random crystal orientations in the polycrystalline substrates [21]. On the other hand, the poor polycrystalline state is well improved and highly c-axis oriented nitride thin films are obtained when an amorphous layer having around 1 μm thickness is inserted between the nitride thin films and such polycrystalline substrates [22] [25]. Therefore, the similar effect on the crystallinity is considered to be occurred in the case of the GaN thin film grown on the amorphous-carbon-coated graphite substrate.…”

“…In addition, growths of the nitride semiconductor thin films on polycrystalline substrates such as metal substrates and/or metal thin film deposited glass substrates have been also reported [21]- [24]. The polycrystalline structures of the films grown on the polycrystalline substrates were successfully improved to highly c-axis oriented structures by inserting an amorphous intermediate layer which has enough thickness to isolate the effect of the polycrystalline substrate [22] [25].…”

TEM study of GaN-based nanopillar-shaped-crystals grown on a multicrystalline Si substrate

“…[12][13][14] There have been some significant results reported about the growths of the GaN-related semiconductors on amorphous and/or polycrystalline substrates. [15][16][17][18][19][20][21][22] Moreover, processes for LEDs based on GaN-related semiconductors grown on such non-single crystalline substrates have been reported. 23,24) Thus, public interest in applications of nonsingle crystalline substrates for fabrications of novel optoelectronic devices has been growing, however, there are still plenty of problems for further improvement.…”

Effect of SiO2(1.2 µm)/Ti-Foil Substrate Nitridation on GaN Thin Films Grown by Reactive Evaporation Method

“…Gallium nitride (GaN) has attracted great interest due to its valuable application in photoelectric devices. [1][2][3] Single crystal wafers such as sapphire (-Al 2 O 3 ), GaAs, LiGaO 2 and GaN are generally used as substrates for the growth of the GaN thin films. 4) However, these wafers are expensive and limited in size.…”