Laser diodes (LDs) and diode bars having output powers from a few to tens and hundreds of watts require effective heat removal from the active region of the semiconductor heterostructure. It was shown as early as the late 1960s that diamond crystals can be employed as effective heat sink bases for semiconductor lasers. The thermal conductivity of diamond is one of its most remarkable properties. It exceeds by several folds the thermal conductivity of all other solid materials: metals, semiconductors and dielectrics , including copper, which is used most frequently to remove heat in electronics. Diamond is also applied as a highly effective heat sink material in other semiconductor devices, such as avalanche and Gunn diodes, The use of diamond in commercial applications is however limited by its relatively high cost and a number of technical problems.
In this work, with the aim of solving these problems we analyze the possibility of using synthetic and natural, single-crystal and polycrystalline diamond and its thermal performance. The advantages of diamond as a heat sink material manifest themselves only when its thermal resistance Rth exceeds that of all other components of the device . As will be shown below, this can be achieved by using a new approach to the moralization of diamond heat sink bases (DHSs), which ensures sufficiently good and uniform adhesion of the metallic coating, and by developing an appropriate mounting process for diode structures.
Super hard materials, including diamond, are composed of atoms in stable electronic configurations and are nonreactive with most metals and solders. Adequate adhesion to diamond might be offered by metals that have high chemical affinity for carbon, preferably those that form carbides possessing metallic bonding and metallic properties (chromium, titanium, niobium, zirconium, tantalum, molybdenum and tungsten). The development of a process for applying high-adhesion metallic coatings to diamond is an important practical issue, which is far from being resolved.
Using multifunctional ion-beam and magnetron sputtering systems, we have developed chemical and vacuum techniques for producing metallic coatings firmly adherent to various surfaces, with application to copper and diamond heat sinks for diode lasers. Conditions have been optimized for mounting diode lasers and bars using the proposed metallization processes, and significant improvements in the output parameters of the devices have been achieved. The power output of CW laser diodes on diamond heat sinks increases by up to a factor of 2, the linear (working) portion of their power-current characteristic becomes markedly broader, and their slope efficiency increases by a factor of 1.5-2.0 relative to that of lasers on copper heat spreaders. The use of diamond heat sinks extends the drive current range of pulsed diode bars by a factor of 2-3 and enables them to operate at more than one order of magnitude longer pump pulse duration (up to milliseconds) when the pulse repetition rate is at least 10 Hz.
CSMH has been committed to the research and development and production of diamond materials. Now it has products such as diamond heat sink sheet,diamond wafer, diamond window to provide customers with a comprehensive thermal management solution.
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