Development of High Threshold Voltage Control Nitride Semiconductor Power Transistor on Silicon Substrate by NEC
NEC and NEC Electronics made an announcement on development of high threshold voltage control gallium Nitride power transistor on a silicon substrate. The new product has improved the control and suppression of electrical currents when electrical power is off which is a required feature for the safe operation of consumer electronics as well as IT devices.The new transistor comes with a new structure for the layer just beneath the gate electrode, resulting in improvement in controllability of threshold voltage that intercepts electrical current as well as enabling the achievement in low power loss, high speed switching and high temperature operations. Power transistors are responsible for converting electrical power and serves as a controlling element in various applications ranging from consumer electronics to industrial machinery. The current transistors are made of two layer structure which consist of an AlGaN electron supply layer and GaN channel layer which features a great amount of variation in threshold voltage which occurs due to differences in the thickness of AlGaN electron supply layer under the gate, to alleviate this problem, a high precision etching process is required in order to reduce the variation of threshold voltage and at the same time to stabilize normally-off characteristics. On the other hand, the new transistors come with a five layer structure which make it possible for these transistors to control threshold voltage at a high degree of precision through reduction of the threshold voltage’s dependence on the thickness of the electron supply layer. This was made possible through introduction of electric charge neutralization layer, the “Piezo” neutralization layer with in the electron supply layer as well as introducing the buffer layer beneath the channel layer. This structure would enables uniform manufacturing of nitride semiconductor power transistors that achieve normally-off characteristics at a low cost.