Accurate monitoring: ultra-high sensitivity diamond diode temperature sensor

The stability of the device largely depends on the operating temperature. Due to factors such as energy dissipation and insufficient heat dissipation, power devices may fail due to overheating.It is crucial to use advanced temperature sensors to monitor the temperature of the equipment to ensure its stable operation. Among various types of temperature sensors, silicon diode temperature sensors (DTSs) have become the most cost-effective sensors due to their reasonable sensitivity, high precision, and chip integration. However, due to the narrow bandgap of silicon (1.12 eV at 300 K) and high intrinsic carrier concentration, the temperature sensing range of silicon DTSs cannot exceed 500 K. The main drawback of silicon DTSs is their low thermal sensitivity (approximately 2.5 mV/K).

Diamond has a wide bandgap (5.45 eV at 300 K), low intrinsic carrier concentration, high critical electric field, and high thermal conductivity, making it an ideal material for power devices and large-scale temperature sensing applications. In addition, the high excitation energy of boron atoms in diamond (0.37 eV) leads to severe incomplete ionization at room temperature, especially under low doping conditions. This high resistance will rapidly decrease with increasing temperature, as more boron atoms will undergo ionization at higher temperatures. Therefore, low doped diamond is very sensitive to temperature changes and can achieve high sensitivity temperature sensing.

In order to achieve high sensitivity temperature sensing, a low doping drift layer (boron concentration of 1 × 1015 cm-3) was epitaxially grown on a high boron doped diamond substrate (boron concentration of 1 × 1019 cm-3) by microwave plasma chemical vapor deposition (MPCVD). The temperature sensing performance of the diode was evaluated by testing the relationship between its forward voltage and temperature within the range of 298-664 K. The test results are shown in Figure 1. The test results show that under the working current of 10-3 A, the sensitivity of the diode temperature sensor is 22.68 mV/K (298-468 K) and 9.92 mV/K (468-664 K), respectively.

Figure 1 (a) Current voltage test data of the sensor in the temperature range of 298-664 K;

 (b) The relationship between the forward voltage of sensors and temperature under different working currents

CSMH is committed to the research and production of diamond materials, with advanced diamond preparation and processing technology. Currently, it has achieved mass production of 2-inch diamond wafers. Its core products include diamond heat sinks, diamond wafers, diamond windows, diamond heterojunction integrated composite substrates, etc. Currently, it is applied in high-power lasers, new energy vehicles, optical communication, radar, military aerospace and other fields.