Diamond wafers: Ideal heat dissipation materials for semiconductor lasers

With the development of high-power semiconductor lasers, they have been widely used in various fields such as laser communication, laser printing, medical instruments, etc. However, when high-power semiconductor lasers work, a large amount of heat is generated in the active region, which reduces the output power of the laser and shortens its service life. Diamond wafers have high thermal conductivity characteristics, and using them as transitional heat sinks will improve the device's heat dissipation ability, reduce thermal resistance, increase laser output power, and extend laser lifespan.

At present, the main heat dissipation method for semiconductor lasers is through heat sink. High power semiconductor devices generally add transition heat sink on top of copper heat sink. Common transition heat sink materials include aluminum nitride, aluminum oxide, beryllium oxide, tungsten copper alloy, molybdenum copper alloy, etc. The requirements for transition heat sink in high-power semiconductor laser packaging mainly include two aspects:

1. Low thermal resistance: The higher the thermal conductivity of the transition heat sink, the more effective it is to reduce the thermal resistance of the laser.

2. Low heat mismatch: The mismatch between the thermal expansion coefficient of the chip and the transition heat sink generates thermal stress, which can affect the output power, spectral width, reliability, etc. of the semiconductor laser. Therefore, a heat sink material that is more compatible with the thermal expansion coefficient of the laser chip is selected.

Diamond wafers are an excellent choice for heat dissipation materials in semiconductor lasers. Currently, the highest thermal conductivity can reach 2000W/(K · m). Compared to aluminum nitride transition heat sinks with a thermal conductivity of 230/(K · m), the high thermal conductivity of diamond heat sinks can significantly improve the heat dissipation effect of high-power semiconductor lasers as transition heat sinks. When used as a heat sink for high-power semiconductor laser packaging, it exhibits excellent heat dissipation characteristics: on the one hand, it can evenly and quickly diffuse the heat concentrated on the PN junction of the device along the surface of the heat sink; On the other hand, heat can be quickly exported along the vertical direction of the heat sink.

 However, when diamond wafers are used as laser heat sinks, due to their low thermal expansion, difficulty in wetting and welding with metals, they are greatly limited in the assembly and application process with other devices and solder materials. Therefore, it is necessary to solve problems such as surface smoothness, parallelism, metallization, and cutting.

CSMH focuses on diamond production and research，possesses world-class diamond manufacturing processes, and innovates efficient and precise diamond atomic level surface machining methods, reducing the surface roughness of diamond wafers < 1nm. At present, high-power semiconductor lasers using synthesized diamond wafers have been widely used in many fields such as optical communication, laser diodes, power transistors, and electronic packaging materials.