Wide Bandgap Semiconductor Substrates: Current Status and Future Trends

Wide bandgap semiconductors have expanded the scope of device applications beyond those of silicon and gallium arsenide. Exploitation of wide bandgap semiconductors holds promise for revolutionary improvements in the cost, size, weight and performance of a broad range of military and commercial microelectronic and opto-electronic systems. The inherent material properties of silicon carbide, gallium nitride and aluminum nitride make them ideal candidates for high-power, high-temperature electronics, power amplifiers, switches, and shortwavelength light sources. Gallium nitride based semiconductor technology has provided the fundamental basis for a new class of opto-electronics. New electronic device structures based on silicon carbide and/or gallium nitride have demonstrated remarkable performance and are being considered for next generation military radar and commercial wireless applications. Additionally, silicon carbide devices have been demonstrated that exhibit superior high-efficiency power switching capability, potentially leading to new capabilities in power distribution as well as electric vehicle technology. Critical to the realization of these enabling capabilities are the availability of high quality affordable substrate materials. The Department of Defense has invested heavily in bulk growth research and development of silicon carbide, gallium nitride and more recently aluminum nitride. A synopsis of current capabilities and future challenges for commercialization of these materials will be discussed. INTRODUCTION Semiconductor substrates provide the foundation for a multi $100B’s electronics industry. Silicon is currently and will remain the material of choice for the foreseeable future due to the low cost, readily availability, and established device technology and infrastructure. If a device can be made with silicon it will. In spite of the phenomenal progress being made with silicon technology it does have its limitations with respect to temperature, frequency operation and voltage blocking capabilities. As gallium arsenide (GaAs) and indium phosphide (InP) technologies provided the basis for the phenomenal growth in the wireless and telecommunications industries during the late 1980s – 1990s, a new class of semiconductors commonly referred to as “wide bandgap semiconductors” holds promise for continued revolutionary improvements in the size, cost, weight and performance of a broad range of military and commercial microelectronic and optoelectronic applications. Silicon carbide (SiC), gallium nitride (GaN) and more recently aluminum nitride (AlN) have emerged as candidate substrate materials that may overcome the performance limitations of silicon, GaAs and InP. SiC is clearly the most developed material of the three due to materials development efforts initiated in the mid-1980's, and the leadership of one company, Cree, Inc. in the maturation of the materials technology.