Discrete Stark-Like Ladder in Piezoelectric GaInN/GaN Quantum Wells

Abstract

The optical properties and their relation to the electronic bandstructure in Si-doped GaInN/GaN multiple quantum well structures typical for near UV laser diode devices are investigated in photoluminescence, photoluminescence excitation and photoreflection spectroscopies. A set of four evenly spaced levels N 0 Á Á Á N 3 is identified covering the spectral range from the lowest luminescence band (N 3 ) to the GaN barrier energy (N 0 ). The splitting of N 3 and N 2 appears as a discrete splitting rather than a continuous localization process. The level splitting is well described by a Stark-like ladder defined by the multi interface bandoffset DE FeL z across the piezoelectric GaN/GaInN/GaN structure.

Light-emitting diode development on polar and non-polar GaN substrates

“…This discrepancy, D well ¼ E(N 2 )À E(N 3 ), is the equivalent of the well-known experimentally observed Stokes shift in a wide range of studies [10,19]. We developed an explanation by which this offset is a replication of the polarization dipole across the QW-an effect that largely exceeds the quantum confined Stark effect [13,14,20,21]. Fig.…”

“…The separation of mobile charges along the field leads to a lowering of the interband transition energy, which can be well approximated by the quantum confined Stark effect. Our previous experimental evidence suggests an even larger red shift DE ¼ L z P/e r , where L z is the full width of the QW [13,14]. A third aspect of the net polarization of the QW is its local interaction with the screening pair of mobile charges.…”

Origin of the ‘S-shaped’ temperature dependence of luminescent peaks from semiconductors

“…It is known that the increase of the injected electric current can result in the increase of the carrier concentration. On the other hand, the increase of the injected electric current may cause a strength decrease of the effective electric field in the diode due to the screening out effect of the electrically injected carriers on the existing huge piezoelectric field [14][15][16][17][18][19][20]. Since the energetic position of E a is dependent on both the carrier concentration and the magnitude of the effective electric field, it is not difficult for one to understand that the magnitude of E a − E 0 changes with the injected electric current.…”

Piezoelectric Polarization in GaInN/GaN Heterostructures and Some Consequences for Device Design

“…Within quantum wells, the polarization field induces level shift 6) and level splitting 12) which in turn is observed as a multitude of emission lines at different wavelengths. 11,14) 0.51 MV/cm at zero bias voltage with reference to the C electrode (Fig. 2).…”

“…In turn, an electric field in the barriers F b is the direct response to polarization P and fields F w within the wells 10) according to F avg (L w + L b ) = F w L w + F b L b and for thermodynamical equilibrium F w = −F b L b /L w = −2 F b . The observation of the level splitting 11) in the wells, however, suggests that |F w | ≈ |F b |. This leads to the value of the piezoelectrically induced polarization P = − 0 r (F w − F b ) = −e z (0.009 − 0.014) C/m 2 or area charge accumulations of σ = (5.9 − 8.8) × 10 12 cm −2 for Ga 0.85 In 0.15 N on GaN with F b = F 0 .…”