Widegap Column‐ III Nitride Semiconductors for UV/Blue Light Emitting Devices

Abstract

This paper reports on a high-quality AtGaN/GaN double heterostructure (DH) which shows UV emission stimulated by optical pumping at room temperature with low threshold power in both edge and surface modes, and a high-efficiency blue light emitting diode (LED) and UV-LED based on p-n GaN homojunction and A1GaN/GaN DH. The process for the fabrication of LEDs and DH and their characteristics are presented.Demand for a high-power short-wavelength light emitter in the blue, violet, and ultraviolet (UV) regions, such as light emitting diode (LED) and laser diode (LD) has been increasing. Applications of these new devices include new full-color large-scale flat panel display systems, compact and high-density optical storage systems, high-speed printing systems, and small medical and biological apparatuses. Realization of these new devices will require highquality wide-bandgap semiconductor films. Column-III nitrides are promising candidates as materials for fabrication of such short-wavelength light emitters, because the wurtzite polytypes of InN, GaN, and A1N form a continuous alloy system whose direct bandgap ranges from 1.9 eV for InN, 3.4 eV for GaN, and to 6.2 eV for AIN, as shown in Fig. 1.During the two decades before 1985, many pioneering works on these nitrides were conducted on crystal growth and doping, ~-8 on device fabrication and physics, 9 and on physical properties. L~ However, it had been quite difficult to grow high-quality epitaxial nitride films, in particular, with a flat surface free from cracks. This is mainly due to the lack of substrate materials for which the lattice constant and thermal expansion coefficient are close to those of GaN and alloys, n Moreover, it was suggested by many researchers that the column-III nitrides have a strong nonstoichiometry problem. ~2In 1986, we succeeded in overcoming the problems mentioned above and in growing high-quality GaN with a spec-* Electrochemical Society Active Member. On the other hand, optically pumped stimulated emission from GaN needle crystal was achieved at 2 K first by Dingle et al. ~ in 1971, and later at low temperatures by several group s. ~ In 1990, we succeeded, for the first time,~7 in achieving room-temperature UV-stimutated emission from our epitaxial GaN film by optical pumping, as shown in Fig. 2. This emission wavelength of 375 nm is much shorter than those of ZnSe-based II-VI compounds. Khan et aI. I8 achieved the first surface-mode UV-stimulated emission from optically pumped GaN and developed GaN electronic devices,~9 which were grown by this low-temperature-deposited A1N buffer layer technique. Nakamura et al. 2~ developed the low-temperature-deposited GaN buffer layer method for the growth of GaN, the concept of which is essentially the same as that of the A1N buffer layer technique.We found that silicon (St) acts as a donor in nitrides, and the electron concentration of n-type nitride has been controlled, while p-type nitrides had never been realized. In 1989, we succeeded in producing, for the first time, distinct p-t...

Study of GaN films grown by metalorganic chemical vapour deposition

“…Under these growth conditions it was more difficult to achieve a mirror like surface. This can be explained by the fact that the growth rate increases relatively more in the [1] direction then the lateral [01 0] direction. Probably other growth parameters are required in these changed conditions to achieve quasi two-dimensional growth.…”

“…A few possible applications are high density optical data storage, full colour video-screens and even traffic lights. Significant progress in epitaxial growth of GaN has already led to commercially available nitride-based high brightness light emitting diodes [1] [2] and very recently the first GaN blue laser was announced [3]. In spite of this recent success the growth of GaN and its alloys remains a challenge.…”

Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures

“…[1][2][3] While much recent GaN research has emphasized growth of device structures ͑blue LEDs and lasers͒ on various substrates, 4 -6 comparatively little work has concentrated on the microscopic growth processes that are of significance, for example, in the electron cyclotron resonance plasma-assisted molecular beam epitaxial ͑ECR-MBE͒ growth of GaN-related heterostructures. Recently, we have shown 7,8 that it is possible to produce high quality, fully commensurate GaN y As 1Ϫy /GaAs strained-layer superlattices ͑SLS͒.…”

The GaN Growth by a Hot Filament Metalorganic Vapor Phase Deposition Technique

“…The following species were considered to exist in a near equilibrium state in the vicinity of the filament surface: NH 3 2 , NH and N species resulting from this decomposition, at atmospheric pressure, are presented in Fig. 3.…”