Resonant cavity light emitting diode (RCLED) has wide applications in fields such as display lighting and optical fiber communication due to its superior features and lower cost compared with ordinary light emitting diodes (LEDs) and vertical-cavity surface-emitting laser (VCSEL). RCLED with an outgoing wavelength of 650 nm needs to be coupled with optical fiber for plastic fiber communication, the coupling efficiency is related to the far-field distribution of outgoing light of RCLED. In addition, the temperature change will affect the far-field distribution of outgoing light of RCLED. As an important component of RCLED, distributed Bragg reflectors (DBRs) have an important influence on the performance of RCLED devices. Therefore, it is of great significance to study the influence of temperature on DBR characteristics. In this paper, the DBR structure is designed and prepared based on RCLED of 650 nm. The effect of temperature change on the reflection spectrum of DBR is simulated, and the white light reflection spectrum of DBR is tested by the test equipment to verify the correctness of the simulation results.

In order to study the effect of temperature on DBR characteristics, the conclusion is drawn through theoretical simulation, and the experiments are used to verify the conclusion. First of all, the DBR structure based on RCLED of 650 nm is designed, and the material based on DBR must have the characteristic of a high and low refractive index material. In terms of material selection, by considering the absorption of red light and the oxidation of materials, the high and low refractive index materials are selected as Al_0.5Ga_0.5As and Al_0.95Ga_0.05As respectively. After determining the constituent material of the DBR, through the fitting function of the refractive index of Al_xGa_1-xAs material given in "the refractive index of Al_xGa_1-xAs below the band gap: accurate determination and empirical modeling", the relationship between the refractive index of Al_xGa_1-xAs and the incident wavelength, temperature, and the component of Al is obtained. Then we further determine the refractive index of Al_0.5Ga_0.5As and Al_0.95Ga_0.05As at room temperature at 650 nm and select the constituent log of DBR as 30 pairs. Later, the reflection spectrum of the DBR composed of 30 pairs of Al_0.5Ga_0.5As and Al_0.95Ga_0.05As at different temperatures is simulated, and the temperature characteristics of the theoretically simulated DBR are obtained. Finally, the designed DBR structure is prepared by the metal-organic chemical vapor deposition (MOCVD) experiment and tested, and the temperature characteristics of the experimental DBR are obtained and compared with the theoretically simulated results.

Firstly, for the RCLED of 650 nm-based DBR design, in terms of the selection of materials constituting DBR, based on the relationship between the band width of Al_xGa_1-xAs material and Al (Fig. 1), the material with higher refractive index is determined to be Al_0.5Ga_0.5As, and as the component of Al gets higher, the device oxidation is more likely to happen. The material with a lower refractive index is determined as Al_0.95Ga_0.05As. Then, by the fitting function of the refractive index of Al_xGa_1-xAs and the three variables, namely the component of Al, temperature, and incident wavelength (Eq. 3), the relationship between the refractive index of Al_xGa_1-xAs and these three variables is obtained (Fig. 2) at 293.15 K with the incident wavelength of 650 nm. The refractive indices of Al_0.5Ga_0.5As and Al_0.95Ga_0.05As are 3.4386 and 3.1215, respectively; the thickness of Al_0.5Ga_0.5As and Al_0.95Ga_0.05As is determined as 47.258 nm and 52.059 nm, respectively in room temperature. Later, the pairs of DBR are determined as 30 by the relationship between the reflectivity and pairs of the DBR in different material combinations (Fig. 3). Then, according to the theory of thin film transmission matrix, the reflection spectrum of the DBR at different temperatures is simulated (Fig. 4), and it is found that the reflection spectrum of DBR moves towards the long wavelength and then through the central reflection wavelength of DBR at different temperatures (Fig. 5). The temperature drift rate of the central reflection wavelength of DBR is 0.048982 nm/℃. Finally, the designed DBR is prepared through the MOCVD experiment, and the white light reflection spectra at different temperatures are tested (Fig. 6). The redshift of DBR with the temperature is obtained. According to the relationship between the central reflection wavelength of DBR and temperature (Fig. 7), the drift rate of the center wavelength with temperature is 0.049277 nm /℃.

For the far-field distribution of RCLED, the DBR structure based on RCLED of 650 nm is designed, and then the effect of temperature on DBR characteristics is analyzed. Temperature changes the optical thickness of each layer of the DBR by affecting the refractive index of the material Al_xGa_1-xAs of the DBR, thus affecting the reflection spectrum of the DBR. According to the theoretically simulated results, the reflection spectrum of DBR appears redshifted to the long wavelength as the temperature increases, and the temperature drift rate of the reflected wavelength of the DBR is calculated by linear fitting. From the experimental test results, as the temperature increases, the white light reflection spectrum of the prepared DBR also appears redshift phenomenon, and the temperature drift rate of the DBR central reflection wavelength calculated by linear fitting is not much different from the theoretically simulated results, which verifies the theoretical simulation. The analysis of the temperature characteristics of DBR makes the device designed at high temperature realize the wavelength matching between quantum trap and DBR, the conclusion has certain guiding significance for designing VCSEL devices with higher temperature sensitivity.