We report on a novel approach for the contactless, all‐optical study of ambipolar carrier diffusion in single‐crystalline diamond layers. Using interband two‐photon and single photon absorption (at 351 nm and 213 nm), we created a spatially‐modulated free‐carrier light‐induced transient grating and monitored the in‐plane carrier diffusion in a wide range of injected carrier densities (1015cm–3 to 1018cm–3) and temperatures (80 K to 800 K). A drastic decrease of the ambipolar diffusion coefficient from ∼50 cm2/s at low injections to 6–10 cm2/s at high ones was observed at room temperature and even stronger at lower temperatures. The modelling based on bandgap renormalization and electron–hole scattering provided a fit to the injection‐dependent diffusivity. The determined low‐injection ambipolar mobility data for CVD layer were found in a good agreement with electrical time‐of‐flight measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We studied carrier recombination and diffusion in GaN/sapphire templates, (In,Ga)N layers, and (In,Ga)N quantum well structures oriented along the polar [0001], semi‐polar [11‐22], and non‐polar [11‐20] orientations by means of light induced transient grating, differential transmission, and photoluminescence optical techniques. We show that the lifetime of excess carriers drops by orders of magnitude when changing the orientation from polar to non‐polar, both in GaN templates and (In,Ga)N layers. We attribute the shorter lifetime to carrier trapping by extended structural defects that are more abundant in non‐polar grown samples. In addition, we observe pronounced carrier localization effects in the semi‐ and non‐polar layers. We show that thick (In,Ga)N layers inherit the properties of the GaN templates. However, the thin quantum well structures show a lower carrier trapping activity. So, a better electrical quality can be assumed as compared to the thick (In,Ga)N layers. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this article, (100) Ib diamond substrates are pre-treated for different durations in an O 2 /H 2 -plasma, influencing the etching of defects like unepitaxial crystals, flat top hillocks, and pyramidal hillocks [1][2][3]. Such procedure is used to prevent those to incorporate into the ~ 100 m thick CVD diamond film, which is subsequently grown on top. While the surface morphology and structure of substrates and films are studied by SEM, the time-resolved LightInduced Transient Grating (LITG) technique provides information on the excess carrier parameters close to the front surface of the grown layers. This technique is particularly useful as it does not requires a separation of the CVD film from its substrate. It will be shown that O 2 /H 2 -plasma treatments of more than 150 minutes but less than 240 minutes largely reduce the incorporation of defects in the bulk of the grown film. This, in turn, influences the carrier dynamics as measured by LITG, but also the surface roughness and growth rate as shown by SEM.