May 4, 2017: Gallium nitride (GaN), a widely used semiconducting materials, has optoelectronic and mechanical properties, making it useful in many applications, including LEDs.
Four Lehigh engineers have found a new property of GaN—the wear resistance of gallium nitride. Wear resistance approaches that of diamonds, which will open up many applications like touch screens, space vehicles and radio-frequency microelectromechanical systems (RF MEMS), everything that require high speed, high vibration technology.
No studies have been done so far about the tribological properties of GaN that its resistance to the mechanical wear imposed by reciprocated sliding.
The researchers performed dry sliding wear experiments on GaN coatings grown epitaxially with metalorganic chemical vapor deposition (MOCVD) on single crystalline sapphire wafers.
Wear rate is expressed in negative cubic millimeters of Newton meters (Nm). The rate for chalk, which has virtually no wear resistance, is on the order of 10-2 mm3/Nm, while that of diamonds is between 10-9and 10-10, making diamonds eight orders of magnitude more wear resistant than chalk. The rate for GaN ranges from 10-7 to 10-9, approaching the wear resistance of diamonds and three to five orders of magnitude more wear resistant than silicon (10-4).
“When performing wear measurements of unknown materials,” they wrote in APL, “we typically slide for 1,000 cycles, then measure the wear scars; these experiments had to be increased to 30,000 reciprocating cycles to be measurable with our optical profilometer. The large range in wear rates (about two orders of magnitude)…can provide insight into the wear mechanisms of GaN.”
That range in wear resistance, the researchers said, is caused by several factors, including environment, crystallographic direction and, especially, humidity.
The wear resistance of GaN gives the opportunity to replace the multiple layers in a typical semiconductor device with one layer made of a material that has excellent optical and electrical properties and is wear-resistant as well.