Reflectance and Photomodulated Reflectance Studies of Cavity Mode and Excitonic Transitions in an InGaAs/GaAs/AlAs/AlGaAs VCSEL Structure

Photomodulated reflectance study ofInxGa1−xAsKlar1, Rowland2, Thomas3 et al. 1999Phys. Rev. BSelf Cite441120View full textAdd to dashboardCite

“…11 Since real VCSEL's are generally designed to operate near room temperature, the cavity exciton resonance also occurs around 300 K. Unfortunately, previous reflectance studies on VCSEL's have shown that it is very difficult to observe clear excitonic signals in the complex R spectra near 300 K, even in the region of the flat high-reflectance stop band, [17][18][19][20][21] and there is only one report of Rabi splitting at ϳ300 K. 11 This can be overcome using modulation spectroscopy, in particular photomodulated reflectance ͑PR͒, where clear features related to both the cavity mode and QW transitions have been observed in VCSEL structures at room temperature. 20,21 However, to analyze such PR spectra fully, it is essential to be able to fit them with an appropriate line shape model, especially when several oscillatory features overlap, as is the case when the exciton and cavity modes are near to resonance. The theory of PR line shapes is well developed for excitonic transitions in bulk and heterostructure semiconductors ͑see, e.g., Ref.…”

“…So far, the mechanism giving rise to a cavity mode PR signal has been explained only qualitatively in terms of a laser induced modulation of the complex refractive index. 20,21 Here we present a detailed PR study of resonances between the cavity mode and QW excitons, particularly the ground-state exciton, in InGaAs/GaAs/AlAs VCSEL structures. We also focus on developing a model for the PR line shape of these signals.…”

Analysis of reflectance and modulation spectroscopic lineshapes in optoelectronic device structures

“…Previously, we have achieved good leastsquares fits to the R spectra of an InGaAs/GaAs/AlAs/AlGaAs VCSEL structure, in which only two parameters were variedthe relative Ga and In effusion cell fluxes [21]. In that study, the theoretical R features were much sharper than observed experimentally, such as a deeper and narrower CM.…”

“…An arbitrary scaling parameter was needed to account for variations in the light collection efficiency in the R measurements, which affected the overall spectral amplitude. However, unlike the previous VCSEL fitting study [21], the experimental resolution and wafer uniformity meant that it was unnecessary to account for instrumental or positional smearing effects. Fig.…”

“…Such differences may arise because of variations in growth rate through the DBRs, perhaps due to a drift in the substrate temperature, or to the effect of different n-and p-type dopant precursors. To analyse these R spectra we have developed an automated method for finding the optimum least-squares fit [21,23,24].…”