R. A. Skogman

Low pressure metalorganic chemical vapor deposition of AIN over sapphire substrates

In this letter we report the deposition of high quality single‐crystal films of AIN over basal plane sapphire substrates. A conventional low pressure metalorganic chemical vapor deposition (LPMOCVD) system was used for all the growths reported here. We present the results of conventional and switched atomic layer epitaxial (SALE) depositions. Conventional LPMOCVD yielded single‐crystal AIN films at temperatures in excess of 750 °C. The ALE process in contrast produced extremely smooth single‐crystal AIN layers at temperatures as low as 450 °C. To the best of our knowledge this is the lowest ever reported for chemical vapor deposition of single‐crystal AIN. X‐ray and optical characterization data are presented to compare the quality of the material resulting from the two deposition techniques.

Atomic layer epitaxy of GaN over sapphire using switched metalorganic chemical vapor deposition

In this letter we report the first switched atomic layer epitaxy (SALE) of single crystal GaN over basal plane sapphire substrates. A low pressure metalorganic chemical vapor deposition (LPMOCVD) system was used for the epilayer depositions. In contrast to conventional LPMOCVD requiring temperatures higher than 700 °C, the SALE process resulted in single crystal insulating GaN layers at growth temperatures ranging from 900 to 450 °C. The band‐edge transmission and the photoluminescence of the films from the SALE process were comparable to the best LPMOCVD films. To the best of our knowledge this is the first report of insulating GaN films which show excellent band‐edge photoluminescence.

Violet‐blue GaN homojunction light emitting diodes with rapid thermal annealed p‐type layers

In this letter we report the fabrication and optical‐electrical characterization of violet‐blue GaN homojunction light emitting diodes. Rapid thermal annealing at 1150 °C (for 30 s) was used to activate the p‐dopant species (Mg), which resulted in p‐type GaN whose photoluminescence response centered around 438 nm is much stronger than that obtained from material annealed in the growth chamber at lower temperatures (700–800 °C) and a longer time (20 min).

Vertical–cavity stimulated emission from photopumped InGaN/GaN heterojunctions at room temperature

We report the observation of room temperature violet (415 nm) stimulated emission in the vertical cavity mode from photopumped GaN/In0.25Ga0.75N heterojunctions. The InGaN/GaN heterojunction was deposited over sapphire substrates using low‐pressure metalorganic chemical vapor deposition and was of high enough optical quality to achieve room‐temperature stimulated emission. The observed emission intensity was found to be a nonlinear function of incident optical pump power density. At threshold we observe a clear line narrowing of the output optical signal from 20 to 1.5 nm full width at half‐maximum.

Electronic and Optoelectronic Devices Based on GaN-AIGaN Heterostructures

Availability of optoelectronic components operating in the U V-Visible part of the spectrum opens several exciting and important system applications. Solid state ultraviolet and blue-green lasers can increase the optical data storage density of CDROM/WORM and magneto-optical disks by a factor of four. They are also ideally suited for environmental pollutant identification and monitoring. On the other hand, solid state ultraviolet detectors that do not respond to visible or IR radiation are highly desirable for various commercial systems. These include medical imaging, industrial boiler systems, fire/flame safeguard systems around oil and gas installations and several military applications. A key requirement for these ultraviolet laser and sensor devices is the availability of a semiconductor material system with high quality controlled doping and fabrication technology. Al x Ga 1−x N and In x Ga 1−x N for which the direct bandgap can be tailored from the visible to the deep UV is such a material system. Ours and several other research groups (nationally and internationally) have been developing Al x Ga 1−x N materials and processing technologies over the past several years. Recently, by employing innovative approaches, significant advances have been made in heteroepitaxy of Al x Ga 1−x N on sapphire substrates. Also, controlled n and p-type doping has been achieved. Several high performance devices that form the basis of exciting future research have been demonstrated. These include high responsivity visible blind ultraviolet sensors, basic transistor structures and high power blue light emitting diodes. These pave the way for future research leading to exciting products such as blue-green lasers and UV-imaging arrays. The demonstrated transistor structures are foundation for building Al x Ga 1−x N -GaN based high power, high frequency and high temperature electronic components. In this paper, we will summarize some of our recent work and reflect on the potential and the issues in Al x Ga 1−x N-In x Ga 1−x N based device development.

Atomic layer epitaxy of YBaCuO for optoelectronic applications

An MOCVD-based atomic-layer epitaxy process is being developed as a potential solution to the problems of film-thickness and interface-abruptness control which are encountered when fabricating superconductor-insulator-superconductor devices using YBa2Cu3O(7-x). In initial studies, the atomic-layer MOCVD process yields superconducting YBa2Cu3O(7-x) films with substrate temperatures of 605 C during film growth, and no postdeposition anneal. The low temperature process yields a smooth film surface and can reduce interface degradation due to diffusion.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.