Cavity Polaritons in InGaN Microcavities at Room Temperature

Cavity polaritons are observed in InGaN quantum well (QW) microcavities at room temperature. High-quality microcavities are fabricated by the wafer-bonding of InGaN QW layers and dielectric distributed Bragg reflectors. The anticrossing behavior of strong exciton-photon coupling is confirmed by vacuum-field Rabi splitting obtained from reflection measurements. This strong coupling is also enhanced by increasing the integrated oscillator strength coupled to the cavity mode. The oscillator strength of InGaN QW excitons is 1 order of magnitude larger than that of GaAs QW excitons.

Figure 1

Schematic diagram of the fabricated InGaN microcavity with dielectric DBRs. (a) The SiC substrate is removed from the InGaN QW layer with a conventional dry etching technique. (b) The InGaN QW layer is sandwiched between two ${\mathrm{SiO}}_2/{\mathrm{ZrO}}_2$ DBRs deposited on sapphire substrates with a wafer-bonding technique. (c) A smooth and crack-free microcavity is formed.

Figure 2

Reflection spectra of the fabricated cavity in the nonresonant region measured at various positions at room temperature. The dashed line is a guide for the eye. The detuning range in this cavity is $0.2\mathrm{meV}/\mu \mathrm{m}$.

Figure 3

Reflection spectra of InGaN QW microcavities measured at room temperature for various degrees of cavity detuning $\delta =E_{\mathrm{ph}}-E_{\mathrm{ex}}$. (a) A series of reflection spectra from $\delta =-3\mathrm{meV}$ to 4 meV. $E_{\mathrm{ex}}$ (dotted line) was assumed to be 2.807 eV. (b) The dip positions in (a) plotted as a function of the detuning energy $\delta$. The dashed lines show $E_{\mathrm{ph}}$ and $E_{\mathrm{ex}}$.

Figure 4

The reflection spectra of the microcavities with 3 QWs (upper) and 10 QWs (lower) at $\delta =0$. The solid curves show the theoretical calculations with fitting parameters of $\alpha =4\times {10}^5{\mathrm{cm}}^{-1}$ and ${\gamma }_{\mathrm{ex}}=15\mathrm{meV}$.