Growth of InN and InGaN/InN heterostructures for electronic device applications

As a low-bandgap material, InN has a rather low electron effective mass and may therefore be expected to exhibit quite large electron mobility, making it potentially useful as a channel material for HEMTs or bipolar devices. Due to the difficulties in epitaxial growth of InN and the strong surface electron accumulation, carrier densities found InN layers are still quite large. We have grown InN as well as InGaN/InN heterostructures using RF-MOMBE. On c-plane sapphire 500-1000 nm thick InN layers were grown at about 500 C. InGaN/InN structures were realized by adding a thin InGaN cap layer with up to 10% Ga. By AFM we find a well developed step structure with indications for step bunching with step heights of twice the c-lattice constant. HRXRD show good quality InN with rocking widths as low as 400 arcsec for (0002) and (10-15) reflections. Inclusions of metallic Indium are below 0.2%. Hall-effect data result in electron densities in the high 1018 cm-3 and electron mobility up to 800 cm2/Vs. Preliminary measurements on InGaN/InN structures indicate somewhat higher electron densities at similar mobility. Further investigations are underway to reveal a possible 2D behaviour at the InGaN/InN interface