Light emitting diode

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising:

• a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order:
• a substrate of a first conductivity type,
• a bottom confining layer of a first conductivity type,
• an active layer capable of emitting light spontaneously under forward bias conditions,
• a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and
• a semiconductor contact layer of the second conductivity type,
• said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R.sub.B .gtoreq.99%), and
• said top electrode is provided with a centrally located aperture in which is exposed an upper surface of the contact layer, the interface between said upper surface and air overlaying said upper surface forming said top mirror having reflectivity 25% .ltoreq.R.sub.T .ltoreq.99%, preferably 25% .ltoreq.R.sub.T .ltoreq.35%.

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising:

• a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order:
• a substrate of a first conductivity type,
• a bottom confining layer of a first conductivity type,
• an active layer capable of emitting light spontaneously under forward bias conditions,
• a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and
• a semiconductor contact layer of the second conductivity type,
• said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R.sub.B .gtoreq.99%), and
• said top electrode comprises a thin metal layer overlying the contact layer and an optically transparent conductive semiconductor material overlying said metal layer, the conductive semiconductor material is selected from the group consisting of cadmium tin oxide and indium tin oxide, and said metal layer and said conductive semiconductor layer acting simultaneously as the top electrode and the top mirror of said LED, the reflectivity, R.sub.T, of the top mirror being 25%.ltoreq.R.sub.T .ltoreq.99%.

A light emitting diode (LED) comprising:

• a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order:
• a substrate of a first conductivity type,
• a bottom confining layer of the first conductivity type,
• an active layer capable of emitting light spontaneously under forward bias conditions,
• a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and
• a semiconductor contact layer of the second conductivity type,
• said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer,
• wherein said LED further comprises:
• a bottom mirror and a top mirror on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom mirror is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R.sub.B .gtoreq.99%), and
• said top electrode comprises an annular thin metal layer overlying the contact layer, and said top mirror comprises a stack of a plurality of pairs of high index of refraction and low index of refraction layers, said stack overlying that surface of the contact layer which is exposed in the central aperture of the annular metal layer and partially overlapping an edge of the annular metal layer adjacent said aperture, the reflectivity, R.sub.T, of the top mirror being 25%.ltoreq.R.sub.T .ltoreq.99%, preferably 80%.ltoreq.R.sub.T .ltoreq.99%.