Optical high excitation of diamond: phase diagram of excitons, electron–hole liquid and electron–hole plasma

Anomalous Blue Shift of Exciton Luminescence in Diamond

“…Figure a shows a mapping diagram of the temperature-dependent photoluminescence (PL) spectrum of a diamond produced by the high-temperature and high-pressure (HPHT) method excited by a 193 nm deep-UV laser. − (See the Supporting Information for Materials and Methods and Figures S1–S3.) As the temperature changes from 10 to 290 K, the PL spectrum of HPHT diamond exhibits phonon-assisted luminescence characteristics of the FE and EHL, including the phonon replicas of the FE, that is, FE TA , FE TO , FE LO , FE TO+OΓ , and FE TO+2OΓ , and the phonon replicas of the EHL, that is, EHL TO and EHL TO+OΓ , which are similar to those reported in previous research. ,, It can also be seen from Figure a that the temperature dependences of these emission peaks of FE-and EHL-related phonon replicas are quite different as the temperature rises (see Figure for the specific change process): The emission intensity of the former one increases first and then decreases with a blue-shifted trend shown by the peak position (see Figure S4 for the peak position change of FE TO and FE TO+OΓ excitonic peaks as the temperature rises) (i.e., it moves to higher-energy zone), whereas for the latter one, the emission intensity gradually decreases with the peak position, displaying a red-shifted trend (i.e., it moves to lower-energy zone).…”

“…13−15 replicas of the FE, that is, FE TA , FE TO , FE LO , FE TO+OΓ , and FE TO+2OΓ , and the phonon replicas of the EHL, that is, EHL TO and EHL TO+OΓ , which are similar to those reported in previous research. 5,16,17 It can also be seen from Figure 1a that the temperature dependences of these emission peaks of FE-and EHL-related phonon replicas are quite different as the temperature rises (see Figure 2 for the specific change process):…”

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

“…The recombination enhancement at low T can be explained by exciton and biexciton formation. The exciton density is n ex = Δ N 2 / n * at low injections, otherwise , where Δ N FC is free carrier density (here n * = N dos ex exp(− E ex / kT ), and N dos ex = 2(2 πm red kT/h 2 ) 3/2 is the exciton density of states, equal to 2.1 × 10 18 cm −3 at RT), E ex = 80 meV is the exciton binding energy, and m red = 0.19 m 0 is the reduced exciton mass (, where electron and hole effective masses are m e = 0.48 m 0 , m h = 0.31 m 0 , respectively). When n * < Δ N , then most of the carriers are bound to excitons.…”

Optical monitoring of nonequilibrium carrier diffusion in single crystalline CVD and HPHT diamonds under high optical excitation

“…In the T < 150 K range, the discrepancy between the fitting and experimentally observed saturation of D a may be caused by carrier and lattice heating (because of the low thermal capacity of diamond 8). Moreover, contribution of electron hole droplet formation below 173 K in the ∼10 18 – 10 19 cm –3 excitation range 13 cannot be excluded. Further studies of carrier dynamics at high carrier densities and low temperatures are needed to elucidate these effects.…”