A high brightness GaP multicolor LED

A multicolor LED which can emit red, green, and any other colored light between red and green, such as orange and yellow, has been developed. This new LED is fabricated by growing epitaxially a double junction of red and green light emission on one side of a Gap substrate. The four epitaxial layers of Gap, referred to as n
₁
, P
_l
, P
₂
, and n
^{2, are grown by liquid phase epitaxy on the (111)B surface of an n-type GaP substrate. They are doped with Te, Zn, Zn, and S as the carrier dopants, respectively. The P₁ layer and the P₂ and n₂ layers are also doped with oxygen and nitrogen in order to form radiative recombination centers for the red light emission in the P₁ layer and for the green light emission in the P₂ and the n₂ layers. This device has three electrodes, a common p-electrode and two n-electrodes, one for there d light emitting junction, the others for the green light emitting junction. Two kinds of the device, a nonplaner type and a planer type, have been fabricated. In the nonplaner-type device, the common p-electrode is directly formed on the P₁ or the P₂ layer by etching away a part of the nz layer. On the other hand, in the planer-type device, Zn is selectively diffused deep enough to reach the P_z layer, and the p-electrode is formed on the Zn diffused part of the n₂ layer. The diffused region is isolated from the n₂ layer by mesa etching. The n-electrodes are formed on the surface of the n₂ layer, and on the bottom of the substrate in both versions of the device. The red and green lights are emitted by driving the junction (plnl) and (pznz), respectively. Colors which are mixtures of the red and green lights are obtained by driving both junctions simultaneously, and the emitting color can be controlled by changing the ratio of (P₁n₁) current to (P₂n₂) current. The quantum efficiencies of the red and green emissions are 4 percent (2 A/cm2) and 0.4 percent (12.5 A/cm2), respectively, both of which are about the same as those of the high efficiency single color LED's. A variety of possible applications can bes een for them ulticolor LED's. Indicator lamps and displays can have many complicated functions. A matrix display for letters, numbers, and images is also one of the most attractive applications of the multicolor LED.}