OPTICAL-PROPERTIES OF DOPED GAN GROWN BY A MODIFIED MOLECULAR-BEAM EPITAXIAL (MBE) PROCESS ON GAAS SUBSTRATES

Both zinc-blende and wurtzite GaN layers were grown by a modified mole cular beam epitaxy (MBE) method. These layers were grown on semi-insul ating GaAs(100) substrates and doped with silicon and beryllium as n- and p-type dopants. The structure of the materials was confirmed using X-ray diffraction (XRD). Photoluminescence (PL) measurement at 77 K s hows a single sharp emission at 3.473 eV for the wurtzite GaN doped wi th silicon, and this peak is shifted downwards in energy by about 200 meV in the zinc-blende GaN doped with silicon. The donor ionisation en ergy is estimated to be similar to 30 meV. For beryllium in GaN, PL sh ows a broad emission at about 2.55 eV for the wurtzite material, while two lines at 2.90 eV and about 2.2 eV appear in the zinc-blende sampl e. An acceptor ionisation energy for zinc-blende GaN of 200 meV is est imated for the first time.