Influence of the temperature on growth by ammonia source molecular beam epitaxy of wurtzite phase ScAlN alloy on GaN

Due to its large piezoelectric and spontaneous polarization coefficients combined with the possibility of being grown lattice-matched with GaN, wide bandgap ScAlN is becoming a promising material in III-nitride semiconductor technology. In this work, and for the first time, ScAlN growth has been performed by molecular beam epitaxy with ammonia source as nitrogen precursor. High electron mobility transistor heterostructures with a 26 nm thick Sc0.15Al0.85N barrier have been grown on GaN-on-sapphire substrates. The effect of growth temperature, ranging between 620 and 800 C, was carefully investigated. A smooth surface morphology with a mean roughness below 0.5 nm is obtained whatever the temperature while for 670 C the (0002) and (1013) x-ray diffraction rocking curves show minimum full-width at half-maximum of 620 and 720 arc sec, respectively. Furthermore, two-dimensional electron gases with a high density of 3-3.5 x 10(13)/cm(2) were evidenced in the heterostructures grown below 720 C.

Automated summary

For the first time, ScAlN growth has been carried out by molecular beam epitaxy using ammonia as the nitrogen precursor. The study shows that smooth surface morphology with a mean roughness below 0.5 nm can be achieved at any growth temperature. X-ray diffraction rocking curves indicate minimum full-width at half-maximum of 620 and 720 arc sec for (0002) and (1013) crystal planes at a temperature of 670°C. Additionally, high-density two-dimensional electron gases of 3-3.5 x 10(13)/cm(2) were observed in the heterostructures grown below 720°C.