Light-emitting semiconductor device having an overvoltage protector
An LED includes a light-generating semiconductor region having an active layer sandwiched between two confining layers of opposite conductivity types for generating light. A cathode is arranged centrally on one of the opposite major surfaces of the semiconductor region from which is emitted the light. A reflector of electroconductive material is formed on the other major surface of the semiconductor region for reflecting the light back toward the light-emitting surface of the semiconductor region. For protecting the LED against breakdown from overvoltages, a zener diode is employed which takes the form of a baseplate having two semiconductor regions of opposite conductivity types sandwiched between a pair of electrodes in the form of metal layers. The protector baseplate is integrated with the light-generating semiconductor region by joining one of the metal layers to the reflector under heat and pressure, thus serving as both mechanical support and overvoltage protector for the LED.
1. A light-emitting semiconductor device protected against electrical breakdown due to overvoltages, comprising:
(a) a light-generating semiconductor region comprising a first and a second semiconductor layer of opposite conductivity types for generating light, the light-generating semiconductor region having a first major surface and a second major surface, opposite to the first major surface;
(b) a first electrode disposed on the first major surface and electrically connected to the first semiconductor layer of the light-generating semiconductor region;
(c) an electric conductor layer disposed on the second major surface and connected both electrically and mechanically to the second semiconductor layer of the light-generating semiconductor region wherein the conductor layer covers the entire second major surface of the light-generating semiconductor region;
(d) a second electrode electrically connected to the conductor layer; and
(e) an overvoltage protector connected both electrically and mechanically to the conductor layer for protecting the light-generating semiconductor region from overvoltage, wherein the overvoltage protector is in the form of a semiconductor baseplate bonded to part of the second major surface of the light-generating semiconductor region via the conductor layer,
wherein the second electrode is a bump electrode formed on the rest of the second major surface of the light-generating semiconductor region via the conductor layer.
2. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the overvoltage protector is in the form of a semiconductor baseplate bonded to the second major surface of the light-generating semiconductor region via the conductor layer.
3. The overvoltage-protected light-emitting semiconductor device of claim 2 , wherein the semiconductor baseplate is constituted of a protector diode comprising:
(a) a first semiconductor region of a first conductivity type bonded to the conductor layer;
(b) a second semiconductor region of a second conductivity type disposed contiguous to the first semiconductor region; and
(c) a connector for connecting the second semiconductor region to the first electrode.
4. The overvoltage-protected light-emitting semiconductor device of claim 3 , wherein the connector extends over the semiconductor baseplate and the light-generating semiconductor region.
5. The overvoltage-protected light-emitting semiconductor device of claim 3 , wherein the connector extends through a channel cut in the semiconductor baseplate and the light-generating semiconductor region.
6. The overvoltage-protected light-emitting semiconductor device of claim 2 , wherein the semiconductor baseplate is bonded to the conductor layer via a bonding layer of electroconductive material.
7. The overvoltage-protected light-emitting semiconductor device of claim 2 , wherein the semiconductor baseplate is higher in heat conductivity than the light-generating semiconductor region.
8. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the conductor layer is made from reflective material for reflecting the light from the light-generating semiconductor region for emission from the first major surface of the light-generating semiconductor region.
9. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the conductor layer is made from silver or silver-base alloy.
10. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the light-generating semiconductor region further comprises:
(a) an active layer between the first and the second semiconductor layer; and
(c) a multi-sublayered current-spreading layer between the first electrode and the first semiconductor layer of the light-generating semiconductor region, the current-spreading layer being capable of generating two-dimensional electron gas.
11. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the overvoltage protector is a zener diode.
12. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the overvoltage protector is a varistor.
13. The overvoltage-protected light-emitting semiconductor device of claim 1 , wherein the overvoltage protector is a capacitor.
14. A light-emitting semiconductor device protected against electrical breakdown due to overvoltages, comprising:
(a) a light-generating semiconductor region comprising a first and a second semiconductor layer of opposite conductivity types for generating light, the light-generating semiconductor region having a first major surface and a second major surface, opposite to the first major surface;
(b) a first electrode disposed on the first major surface and electrically connected to the first semiconductor layer of the light-generating semiconductor region;
(c) an electric conductor layer disposed on the second major surface and connected both electrically and mechanically to the second semiconductor layer of the light-generating semiconductor region;
(d) a second electrode electrically connected to the conductor layer; and
(e) an overvoltage protector connected both electrically and mechanically to the conductor layer for protecting the light-generating semiconductor region from overvoltage wherein the overvoltage protector is in the form of a semiconductor baseplate bonded to the second major surface of the light-generating semiconductor region via the conductor layer, wherein the conductor layer and the semiconductor baseplate are transparent to the light generated by the light-generating semiconductor region,
wherein the first electrode on the first major surface of the light-generating semiconductor region is made from reflective material for reflecting the light for emission through the semiconductor baseplate.