Group III-nitrides materials have found broad usage in optoelectronic applications thanks to their wide bandgap range, electron mobility, and resistance to radiation. Higher indium incorporation has shown promise for enabling longer wavelength optoelectronic devices and possibly improve current device efficiencies. However, the increase of indium complicates the way nitrogen can be chemically incorporated into these materials, which remains as a challenge for the field.

Clinton et al. report new ways to optimize a technique called plasma-assisted molecular beam epitaxy (PAMBE) to reduce the amount of damage done to indium nitride (InN) films while producing them. Tests using a Langmuir probe and photoluminescence spectroscopy showed that the amount of damage done to InN films can be decreased up to 74% by optimizing the nitrogen flow and the applied plasma power.

Increasing the flow and thus pressure parameters provides a way to prevent plasma particles with too much kinetic energy from damaging a sample, said author W. Alan Doolittle.

“It’s been folklore in the field that operating at lower power was somehow supposed the lower damage. It turns out that has very little effect on the damage at all,” he said. “Instead, increasing the pressure is like running in a crowded room. If you have a lot of people around you, you can’t get going very fast.”

Forming group III-nitrides that contain significant amounts of indium requires incorporating nitrogen at low temperatures, which is unfeasible with most techniques. Choosing InN for the study due to its sensitivity, Clinton et al. were able to monitor the plasma-related damage during PAMBE, and found that PAMBE can help avoid the incompatibility between the incorporation of indium and nitrogen.

Doolittle said they plan to continue work optimizing indium-based group III-nitrides for optoelectronics.

Source: “Observation and mitigation of RF-plasma-induced damage to III-nitrides grown by molecular beam epitaxy,” by Evan A. Clinton, Ehsan Vadiee, M. Brooks Tellekamp, and W. Alan Doolittle, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5097557.