Abstract:
The plasma-enhanced chemical vapor deposition (PECVD) method is used to fabricate planar Fabry-Perot microcavities (MCs) with an active region emitting light at the boundary between the visible and infrared (IR) spectral ranges. The MCs comprise an $a$-Si$_{1-x}$C$_x$ : H active layer with an increased carbon content and distributed Bragg reflectors (DBRs) constituted by alternating nonemitting $a$-Si$_{1-x}$C$_x$ : H/$a$-SiO$_2$ layers. The active layer and the DBRs are grown in a single technological cycle. Owing to the high optical contrast and low absorption of the layers constituting the DBRs, a high $Q$ factor of the microcavities ($Q$ = 316) and high emission directivity from the MCs for three pairs of layers in the DBRs are achieved. The intensity of the room-temperature photoluminescence exceeds by two orders of magnitude the emission intensity of an identical $a$-Si$_{1-x}$C$_x$ : H layer without DBRs. Comparison of the experimental transmittance spectra and those calculated by the transfer-matrix method with consideration for dispersion of the real and imaginary parts of the refractive index of $a$-Si$_{1-x}$C$_x$ : H is used to estimate the degree of systematic deviation of the layer thicknesses in the DBRs and to determine the upper limit of the absorption coefficient in $a$-Si$_{1-x}$C$_x$ : H layers.
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