0741-3106 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/LED.2017.2714865, IEEE Electron Device Letters EDL-2017-05-0735.R1 1 Abstract—Silicon carbide (SiC) power devices have been commercialized up to 1.7 kV with operating temperatures up to 573 K. The temperature limitations of SiC devices are generally derived from limitations in packaging and a lack of information on safe operating temperature regimes. Therefore, it is highly desirable to develop reliable temperature sensing techniques that can better take advantage of the SiC devices in high power applications. In this work, ten gallium nitride (GaN)-on-SiC heterojunction diodes, aiming at high power and high temperature sensing applications, were fabricated using a concentric ring geometry. These sensors can be monolithically integrated into GaN-on-SiC RF/Microwave power devices with fast switching frequency and high power density. The temperature dependent characteristics of the forward voltage drop at fixed current (VD– T) of these heterojunction devices and their sensitivities (mV/K) are comprehensively characterized in a temperature range from 300 K to 650 K. These devices exhibit a high degree of linearity in their VD–T characteristics, which indicates the potential to be used as temperature sensors up to 650 K. Index Terms—Gallium nitride; heterojunction diode; silicon carbide; temperature sensor. I. INTRODUCTION ccurate knowledge of the junction temperature (Tj) of a power semiconductor device is critical to its thermal management, especially in high power and high temperature applications. Both direct and indirect methods can be utilized to obtain the device junction temperature [1], [2]. Commonly used direct junction temperature sensing techniques include: optical methods, physically contacting methods, and on-die temperature sensing methods. Optical methods using an infrared camera and physically contacting methods, i.e., adding contact temperature detectors to the power devices, are widely used to obtain the Tj information. However, due to the slow response, these methods are ill-suited for applications that require high bandwidth Tj sensing. With modern device fabrication technology, a small p- n junction diode can be made on the same substrate as the power Manuscript received December 7, 2016. This work was supported in part by the Department of Energy under Grant DE-SC0016485 and the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (Grant No. LAPS17021). S. Madhusoodhanan, S. Sandoval, Y. Zhao, and Z. Chen are with the Department of Electrical Engineering, University of Arkansas, Fayetteville, AR device, such that the diode’s quasi -linear voltage-temperature (VD–T) characteristics can be utilized for Tj sensing [2] with a significantly faster dynamic response [3]-[5]. Indirect junction temperature sensing can be achieved by using the correlation between the junction temperature and the semiconductor electrical properties [6]. Indirect methods can extract the Tj information from the thermo-sensitive electrical parameters of the device itself, e.g., the temperature dependent on-state resistance (Ron) of the MOSFET. However, the temperature dependent variation of the on-state VDS and IDS, which are required to determine Ron, is small. Accurate voltage and current measurement as well as extensive calibration are usually needed. Due to the well-established fabrication processes and low cost, silicon (Si) is by far the most commonly used material for power semiconductor devices. Fast development of wide bandgap semiconductor devices has led to the successful commercialization of high-voltage silicon carbide (SiC) power MOSFETs, which operate up to 1.7 kV with operating temperatures up to 573 K (300 ° C). The temperature limitations of SiC devices come from both limitations in packaging and lack of information on safe operating temperatures [7]-[9]. As reported in [8], a 4H-SiC based p-i-n diode temperature sensor was designed and fabricated to measure temperature up to 573 K with a maximum sensitivity of 2.66 mV/K. In the same work a high performance 4H-SiC based Schottky diode sensor with sensitivity of 5.11 mV/ o C was demonstrated. G. Brezeanu et al. reported a SiC-based high temperature sensor with a capability to measure temperature up to 175 o C and a sensitivity of 1.52-2.13 mV/ o C [9]. In [10], a highly linear proportional-to- absolute temperature voltage source was demonstrated using monolithically integrated gallium nitride (GaN)-based devices. As reported in [11], a 4H-SiC p-n diode temperature sensor was designed and fabricated to measure temperature up to 600 o C with a maximum sensitivity of 3.5 mV/ o C. In this work, p-type gallium nitride (p-GaN) on n-type SiC heterojunction diodes are fabricated and comprehensively 72701 USA (e-mail: smadhuso@email.uark.edu; sxs104@uark.edu; yuezhao@uark.edu; chenz@uark.edu); M. E. Ware is with the Department of Electrical Engineering and the Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR 72701 USA (e-mail: meware@uark.edu). S. Madhusoodhanan, S. Sandoval, Y. Zhao, Member, IEEE, M. E. Ware, Member, IEEE, Z. Chen, Member, IEEE A Highly Linear Temperature Sensor Using GaN-on-SiC Heterojunction Diode for High Power Applications A