Considerations towards a Nitride Semiconductor Substrate Roadmap

Keywords: Gallium Nitride, Aluminum Nitride, LED, Laser Diode, Substrate

E. Preble, R. Metzger, T. Paskova, G. Mulholland, N. Biswas, and K. Evans
Kyma Technologies, Inc., 8829 Midway West Road, Raleigh, NC 27617 USA

Abstract
Nitride semiconductor devices are enjoying explosive commercialization for applications based on blue, green, and white LEDs, as well as ultraviolet (UV) detectors and violet laser diodes. New applications are opening up including those based on UV LEDs, power switching devices, and high frequency electronics. Additionally, several new devices are in the R&D stage such as terahertz emitters and quantum cascade lasers. The market for nitride semiconductor devices today is ~$8B and is expected to surpass $60B over the long term.
Accompanying the growing market success of nitride semiconductor devices is the continuous drive to reduce device cost and improve performance. Historically the question of what substrate to use was simple to answer. Today determining the best substrate approach requires a complex analysis, due to the growing number of substrate choices and their continuously evolving maturity levels.
A roadmap will be presented which forecasts the evolution of preferred substrate compositions and forms [size (2” through 8”), type (e.g., template or bulk), orientation (c-plane, m-plane, etc.] over time for each major nitride semiconductor device application including vertical and lateral power switching devices, high frequency transistors, light emitting diodes of differing wavelengths, and laser diodes. Consideration will be given to bulk Al2O3, Si, SiC, and ZnO, as well as both bulk and template versions of AlGaN, AlN, and GaN.
The roadmap will include a comparative analysis of the cost of substrate manufacturing for each substrate choice as well as the potential impact on device manufacturing cost, including often overlooked elements of downstream process yield and throughput enhancement. Focus will be placed on high volume LED manufacturing with comparison of relative advantages of certain GaN, AlGaN, and AlN bulk and template products for improved LED device performance and reduced LED device manufacturing cost. Recent materials and device developments obtained on Kyma’s substrates for visible LED applications will be presented in support of the roadmap. This includes demonstration of increased LED device yields via 5 to 15% increase in brightness and 50 to 70% defect density reduction just by adding a low-cost thin PVD AlN layer to flat/unpatterned sapphire substrates.

Paper 8b.1.pdf