Abstract
Thermal and electrical properties of aluminum nitride (AlN) epilayers grown by chemical beam epitaxy (CBE) were investigated. A high growth rate of 5.9 ± 0.4 µm/h was achieved using trimethyl aluminum and ammonia as group III and V precursors, respectively, at a growth temperature below 600 °C. The thermal conductivity and breakdown field of 10 µm thick AlN epilayers were measured to be 57 W/(m.K) and 1.04 106 V/cm, respectively. These results demonstrate the potential of CBE as an alternative growth method for the development of thick AlN layers in high power device applications.
Highlights
Aluminum nitride (AlN) layers have been widely used in optoelectronic applications, such as high electron mobility transistors (HEMT),1 light-emitting diodes (LED),2 and microelectromechanical systems (MEMS)3 because of their outstanding properties, namely wide bandgap, dielectric properties, and high thermal conductivity
Low growth rates are commonly seen in high quality III-N, which is impractical for the thick AlN required for isolation layers, supporting the use of reactive magnetron sputtering in industrial settings
We presented the electrical and thermal characteristics of the thick AlN epilayers grown by chemical beam epitaxy (CBE) at 550 ○C and 600 ○C
Summary
Aluminum nitride (AlN) layers have been widely used in optoelectronic applications, such as high electron mobility transistors (HEMT), light-emitting diodes (LED), and microelectromechanical systems (MEMS) because of their outstanding properties, namely wide bandgap, dielectric properties, and high thermal conductivity. AlN is commonly used as a buffer layer for the growth of high-quality III-nitride structures leading to exceptional performances.. Because of the miniaturization of the microelectronic devices and the simultaneous increase of power, high local thermal heating occurs in high power devices. Power device performances are limited to the breakdown voltage, which occurs when the high electric field reaches the Si substrates underneath the gate–drain region of the devices in high power GaN transistors grown on Si, for example.. It is crucial to overcome these issues with the use of materials that ensure heat dissipation and at the same time prevent breakdown through the substrate. The properties of these materials do not ensure good thermal evacuation and high breakdown simultaneously. The thermal conductivity and the breakdown field of AlN layers are affected by several parameters, most of them related to various crystal imperfections, such as grain size, impurities, and dislocations
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