Mg Doping of N-Polar, In-Rich InAlN.

Metal organic chemical vapor deposition was used to grow N-polar In0.63Al0.37N on sapphire substrates. P-doping was provided by a precursor flow of Cp2Mg between 0 and 130 nmol/min, reaching a Cp2Mg/III ratio of 8.3 × 10-3. The grain structure of 360 nm thick InAlN was spoiled by pits after introducing a flow of CP2Mg at 30 nmol/min. The surface quality was improved with a flow of 80 nmol/min; however, detrimental deterioration appeared at 130 nmol/min. This correlated with the XRD shape and determined density of dislocations, indicating a phase separation at the highest flow. Degenerated n-type conduction and a free carrier concentration of ~1019 cm-3 were determined in all samples, with a minor compensation observed at a CP2Mg flow of 30 nmol/min. The room temperature (RT) electron mobility of ~40 cm2/Vs of the undoped sample was reduced to ~6 and ~0.3 cm2/Vs with a CP2Mg flow of 30 and 80 nmol/min, respectively. Scattering at ionized acceptor/donor Mg-related levels is suggested. RT photoluminescence showed a red shift of 0.22 eV from the virgin 1.73 eV peak value with Mg doping. Mobility degradation was found to be the main factor by InAlN resistivity determination, which increased by two orders of magnitude, approaching ~0.5 Ωcm, at the highest Cp2Mg flow.

GaAs Nanomembranes in the High Electron Mobility Transistor Technology.

A 100 nm MOCVD-grown HEMT AlGaAs/InGaAs/GaAs heterostructure nanomembrane was released from the growth GaAs substrate by ELO using a 300 nm AlAs layer and transferred to sapphire. The heterostructure contained a strained 10 nm 2DEG In0.23Ga0.77As channel with a sheet electron concentration of 3.4 × 1012 cm-2 and Hall mobility of 4590 cm2V-1s-1, which was grown close to the center of the heterostructure to suppress a significant bowing of the nanomembrane both during and after separation from the growth substrate. The as-grown heterostructure and transferred nanomembranes were characterized by HRXRD, PL, SEM, and transport measurements using HEMTs. The InGaAs and AlAs layers were laterally strained: ~-1.5% and ~-0.15%. The HRXRD analysis showed the as-grown heterostructure had very good quality and smooth interfaces, and the nanomembrane had its crystalline structure and quality preserved. The PL measurement showed the nanomembrane peak was shifted by 19 meV towards higher energies with respect to that of the as-grown heterostructure. The HEMTs on the nanomembrane exhibited no degradation of the output characteristics, and the input two-terminal measurement confirmed a slightly decreased leakage current.