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TDI Achieves Next Step in Gallium Nitride Substrate Materials with Sampling of Thick P-type GaN Substrates |
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Source/Type: Company News Releases TDI
Achieves Next Step in Gallium Nitride Substrate materials with Sampling of
Thick P-type GaN Substrates October 22, 2002... Silver Spring, Maryland, USA... Technologies and Devices International, Inc., a privately held Maryland corporation (TDI), today announced the achievement of another major breakthrough in Gallium Nitride (GaN) compound semiconductor material growth technology by demonstrating 2-inch diameter GaN templates with p-type electrical conductivity. GaN is the compound semiconductor material used for the fabrication of blue spectrum (blue, green, and ultra violet (UV) and white) light emitting diodes (LEDs), laser diodes (LDs) and high-frequency/high-power transistors. While the availability of n-type GaN material has been progressing, the lack of availability of cost effective thick p-type material has hampered development and commercial availability of many types of advanced devices. As detailed in the Supplemental Information, attached, test data from independent evaluators confirms the importance of this technology breakthrough. The p-type GaN template consists of a sapphire substrate and high quality, highly doped, thick p-type GaN epitaxial layering that is grown by Hydride Vapor Phase Epitaxy (HVPE). The concentration of electrical carriers (holes) in the GaN layer can be varied in a wide range from 1016cm-3 to 1018 cm-3. Based on current industry reported data, only n-type thick GaN layers have been grown by HVPE whereas, the industry has been long awaiting p-type material. “This is the first sampling of p-type GaN templates by HVPE technology. The well-recognized benefits of GaN HVPE growth technology have included low production cost, high material quality, and high growth rate. Combining that with p-type doping capability opens an opportunity to design, develop, and fabricate novel GaN devices that were not previously possible”, points out Vladimir Dmitriev, President and CEO of TDI. “Until now, lack of p-type GaN substrate materials has been a very real and, thereby, a limiting factor for realizing many new and important GaN device designs. TDI’s sampling of p-type templates, using our patented HVPE technology opens a new avenue for GaN device development”. Realizing the importance of getting these into the merchant market as quickly as possible, TDI is planning to move p-type GaN templates into large-volume production in the first quarter of the year 2003. “Our experience in mass production of n-type GaN templates shows that it is a realistic goal, “ confirms Dr. Dmitriev. TDI has already begun shipping test samples of p-type GaN templates to prospective customers towards this goal. About TDI TDI was founded in Gaithersburg, MD in 1997 as a new independent business. The company is a privately owned developer and manufacturer of novel compound semiconductor materials including GaN, aluminum nitride (AlN) and silicon carbide (SiC). In addition to bulk and epitaxial GaN projects, TDI is developing various compound semiconductor materials and devices, primarily for applications in short wavelength optoelectronics and RF power electronics. For more information, contact: TDI, Inc. Supplemental Information Substrate issues in GaN-based device engineering One of the main issues in GaN device technology has long been the lack of suitable lattice-matched substrates. True bulk GaN is still in the initial stages of becoming commercially available on the open market, and as such, will be regarded as rather expensive in these early stages of development. Currently, GaN-based devices are primarily fabricated on either sapphire or silicon carbide substrates. However, each of these popular substrates are a “lattice-mismatch” to GaN devices which negatively influences both performance and cost factors, along with the technological difficulties of the device manufacturing process. The way around these problems is to, instead, use GaN templates as the substrate material, which provides device designers with a lattice-match for their device structures. GaN templates can be used for wide variety of GaN devices including HEMTs, photo detectors, power switches, lasers, but the largest immediate application is blue/green/UV LEDs. TDI is manufacturing and selling n-type GaN-on-sapphire templates as the substrates of choice for GaN-based LEDs. These substrates have significantly simplified LED growth technology, reduced LED growth time, and increased LED production throughput without increased capital expenditure. P-type material issue in GaN technology GaN and related compound semiconductor materials, such as AlGaN alloys, have been fully recognized as excellent candidates for blue light emitters and advanced power communication electronics since 1970. However, commercialization of GaN-based semiconductor devices became a reality only after the demonstration of GaN materials having p-type electrical conductivity about 12 years ago. In order to fabricate electronic devices such as light emitting diodes (LEDs) or laser diodes (LDs), semiconductor materials of both n-type electrical conductivity (in these materials carriers of electric charge are electrons) and p-type electrical conductivity (in these materials carriers of electric charge are holes) were required. Development of GaN materials with p-type electrical conductibility made it possible to fabricate blue, green, and UV LEDs and blue/UV LDs using GaN technology. Two types of epitaxial processes, metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were demonstrated to be capable of producing p-type GaN layers for these devices. While able to grow high quality thin GaN layers suitable for some device structures, due to low growth rate characteristics, these epitaxial methods fail to produce thick GaN films that are needed for more novel devices. A competing epitaxial method that has proven to be the technology of choice for fabrication of high quality thick GaN films is Hydride Vapor Phase Epitaxy. With a growth rate from 20 to 100 times higher than that for MOCVD or MBE, the HVPE technology is the accepted cost-effective method for fabrication of GaN templates and freestanding GaN wafers. However, only n-type GaN thick layers grown by HVPE had been so far reported. This is the first demonstration of p-type GaN templates by HVPE technology. The well-recognized benefits of GaN HVPE growth technology have included low production cost, high material quality, and high growth rate. Combining that with p-type doping capability opens an opportunity to design, develop, and fabricate novel GaN devices that were previously not possible. Material evaluation of p-type GaN templates fabricated at TDI has been performed at a number of academic and industrial institutions. Results of independent material evaluation “The results of material characterization performed on Accent’s wide bandgap ECV profiler showed a thick layer of highly doped p-type GaN material grown on sapphire substrates at TDI” said Dr. Colm Mac Mahon, Application Engineer at Accent Optical Technologies. |
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Copyright © 2002 TDI, Inc. |