MOVPE is the method of choice in industry and research for the fabrication of high-quality epitaxial III-N films and heterostructures for devices . The optimization and control of growth parameters allows obtaining growth rates as slow as 0.05 nm/s, which is comparable to the growth rates obtained by molecular beam epitaxy (MBE).
Our research topics in the field of III-N deal with the optimization of ternary alloys, the improvement of the electronic properties of III-N codoped with Si (n-type ) and Mg (p-type), the growth of functional heterostructures (LEDs, Bragg reflectors) for opto-electronic devices, and the growth of low-dimensional structures doped with TM ions for magneto-optical measurements.
Rashba spin-orbit coupling in wurtzite n-GaN:Si
Millikelvin magnetotransport studies are carried out on heavily n-doped wurtzite GaN:Si films grown on semi-insulating GaN:Mn buffer layers by metal-organic vapor phase epitaxy. The dependence of the conductivity on magnetic field and temperature is interpreted in terms of theories that take into account disorder-induced quantum interference of one-electron and many-electron self-crossing trajectories. The Rashba parameter αR=(4.5±1) meV Å is determined, and it is shown that in the previous studies of electrons adjacent to GaN/(Al,Ga)N interfaces, bulk inversion asymmetry was dominant over structural inversion asymmetry. The comparison of experimental and theoretical values of αR across a series of wurtzite semiconductors is presented as a test of current relativistic ab initio computation schemes. Low-temperature decoherence is discussed in terms of disorder-modified electron-electron scattering.
Polarization doped 3-dimensional electron slab in graded AlGaN
We have recently shown the achievement of polarization induced high n-type doping of AlxGa1-xN by growing a 3D-electron slab (3DES) grown on a n-GaN:Si reservoir . The 3DES is made out of a graded AlxGa1-xN layer with variable Al concentration from 0 to 37%. These degenerate AlxGa1-xN layers open perspectives for the fabrication of efficient electrodes in nitride-based deep UV-LEDs, DBRs, transistors and spin devices.
- Figure 2: Graded AlxGa1-xN 3DES with high carrier density and high mobility .