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HomeResearch MOVPE of III-Nitrides

MOVPE of III-Nitrides

MOVPE is the method of choice in industry and research for the fabrication of high-quality epitaxial III-N films and heterostructures for devices [1]. 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.


(a) Magnetoconductivity at T<1.5 K
   
(b) Phase coherence ength obtained from the fitting of magnetoconductivity data
   
(c) Rashba parameter αR as a function of the harmonic average photon number Z
Figure 1

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 [2]. 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 [2].

References

  1. H. Morkoc, Handbook of Nitride Semiconductor and Devices, Wiley-VCH (2008)
  2. R. Adhikari et al. Appl. Phys. Lett. 108 (2016)
JKU Institute of Semiconductor and Solid State Physics, Altenbergerstr. 69, 4040 Linz, Austria, Tel. +43 732 2468 9639, Fax +43 732 2468 8650