Carrier recombination and diffusivity in microcrystalline CVD‐grown and single‐crystalline HPHT diamonds

Abstract

We report investigation of carrier recombination and diffusivity in bulk diamonds of different crystalline structure – microcrystalline (MC) CVD‐grown and single crystalline HPHT diamonds. Presence of neutral and positively charged nitrogen and hydrogen defects was determined from NIR and UV–IR absorption spectra. Carrier injection into 1‐mm thick bulk layers was realized by two‐photon absorption at 351 nm wavelength. Carrier lifetimes of 150–330 ns in IIa type HPHT crystals correlated with N density, while the lifetimes in CVD crystal exhibited very fast (80 ps), slower one (3–8 ns), and µs‐duration thermally‐activated (∼1.5 eV) decay components. The initial two components correlated with the grain size at the front and backsides of the MC diamond. Linearly increasing with injection carrier recombination rates were observed in both CVD and HPHT samples at 800 K, and fitted with effective recombination coefficient B = 3–4 × 10−9 cm3/s. Ambipolar mobility and thermal diffusivity parameters in CVD and HPHT bulk crystals were measured by light‐induced free carrier and thermal grating techniques.

Features of free carrier and exciton recombination, diffusion, and photoluminescence in undoped and phosphorus-doped diamond layers

“…This occurs probably due to impact of deep phosphorus-vacancy complexes (PV C ), positioned 3.4 eV below the conduction band [7]. The PV C center can act as effective lifetime killer, as it is the mid-gap defect [18] (nitrogen is also known as lifetime killer [37,38,44,45], providing also weak luminescence in the HPHT substrate).…”

Injection and temperature dependent carrier recombination rate and diffusion length in freestanding CVD diamond

“…Recently time‐resolved nonlinear optical techniques based on light‐induced free carrier absorption (FCA) decay and light‐induced transient grating (LITG) were applied for non‐destructive monitoring of recombination and diffusion processes in diamonds . Injection‐dependent carrier diffusivity was investigated in a wide injected carrier density range (10 15 to 10 18 cm −3 ) and revealed very strong impact of electron–hole scattering and bandgap renormalization at high injections .…”

Crystallite size dependent carrier recombination rate and thermal diffusivity in undoped and boron doped CVD diamond layers

“…In order to study carrier lifetimes and diffusivity at lower injected carrier densities, two-photon carrier injection (2P) by a picosecond laser pulse at 351 nm was recently applied [5]. In this way, excitation of the entire bulk crystal was achieved [6].…”

“…Indeed, lifetimes up to 100 ns were observed in $100 mm large grains of purified CVD diamond at 266 nm excitation wavelength [18]. For comparison, in bulk HPHT diamonds lifetimes were in 150-330 ns range [5]. The large variation of lifetime values (especially on the growth side) might be a consequence of different growth orientation of the grains and consequently different point defect incorporation probability [19].…”