SUPERPOSED MULTIQUANTUM BARRIERS FOR INGAALP HETEROJUNCTIONS

In a visible-light laser using In0.5(Ga1-xAlx)0.5P (0 less-than-or-equal-to x less-than-or-equal-to 1), the conduction-band discontinuity at the interface between the active layer and clad layer is not large enough to strongly suppress carriers overflowing into the clad layer, unlike in the GaAlAs system. This paper uses a multiquantum barrier (MQB) to overcome this problem, and calculates the electron-reflecting powers to determine the characteristics of this suppression. Electron-reflecting powers are calculated for two types of MQB for heterojunction between active and clad layers. One is for a high-power high-temperature laser with an In0.5Ga0.5P active layer, and In0.5Ga0.15Al0.35P clad layer, and a set of superposed MQB's. The other is for a short wavelength (lambda: 586 nm) laser composed of an In0.5Ga0.33Al0.17P active layer, an In0.5Ga0.15Al0.35P clad layer, and a set of superposed MQB's. The results show that the electron energy region where the electron-reflecting power is nearly unity is 0.42 eV for the In0.5Ga0.5P-In0.5Ga0.15Al0.35P MQB set and 0.21 eV for the In0.5Ga0.33Al0.17P-In0.5Ga0.15Al0.35P MQB set. As the former is almost equal to the barrier height of a GaAlAs laser, it is postulated that the carriers are blocked from overflowing in the InGaAlP laser. In addition, since the latter is more than that of the current CW InGaAlP laser, this should also give a short-wavelength (lambda: 586 nm) CW mode DH laser.