Light emitting chip

The disclosure generally relates to a light emitting chip.

In recent years, due to excellent light quality and high luminous efficiency, light emitting diodes (LEDs) have increasingly been used as substitutes for incandescent bulbs, compact fluorescent lamps and fluorescent tubes as light sources of illumination devices.

An LED generally includes a light emitting chip. Electrodes are formed on the light emitting chip for providing power supply to the light emitting chip. However, the electrodes are generally formed on an upper surface of the light emitting chip, which prevents a part of light from travelling to an external environment via the upper surface; therefore, a lighting extraction efficiency of the conventional light emitting chip is disadvantageously affected.

Therefore, a light emitting chip is desired to overcome the above described shortcomings.

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 shows a light emitting chip in accordance with a first embodiment of the present disclosure.

FIG. 2 shows a light emitting chip in accordance with a second embodiment of the present disclosure.

Embodiments of a light emitting chip will now be described in detail below and with reference to the drawings.

Referring to FIG. 1 , a light emitting chip 1 in accordance with a first embodiment of the present disclosure includes a substrate 10 , a first electrode 12 formed on the substrate 10 , a reflective layer 14 formed on the first electrode 12 , a transparent conductive layer 16 overlapped on the reflective layer 14 , a second electrode 17 formed on the transparent conductive layer 16 , a light emitting structure 18 and a connecting layer 19 formed between the light emitting structure 18 and the transparent conductive layer 16 .

The light emitting structure 18 includes a first semiconductor layer 180 , an active layer 182 and a second semiconductor layer 184 . In this embodiment, the first semiconductor layer 180 is an n-type GaN layer, the second semiconductor layer 184 is a p-type GaN layer, and the active layer 182 is a multiple quantum well (MQW) GaN. The light emitting structure 18 is first grown on a temporary substrate (not shown), and then separated from the temporary substrate by laser lift-off, chemical etching or physical etching. A bottom surface of the second semiconductor layer 184 , as shown in FIG. 1 , is connected with the transparent conductive layer 16 through the connecting layer 19 . The connecting layer 19 can be made of heavy doping p-type In 1-x-y Al x Ga y N, p-type In 1-x-y Al x Ga y N with supper lattice structure, or p-doping inversion layer, therefore enhancing ohmic contact between the second semiconductor layer 184 and the transparent conductive layer 16 . The transparent conductive layer 16 can be made of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), magnesium oxide (MgO) or indium gallium zinc oxide (IGZO). The transparent conductive layer 16 is configured for spreading current uniformly into the second semiconductor layer 184 and achieving a uniform light distribution of the light emitting chip 1 .

The reflective layer 14 is made of electrically insulating materials with high reflectivity. The light from the active layer 182 can be reflected by the reflective layer 14 to travel to an external environment, therefore improving light extraction efficiency of the light emitting chip 1 . In this embodiment, the reflective layer 14 is a distributed Bragg reflector (DBR), which can reflect the light with a wavelength ranging from 440 nm to 470 nm. In this embodiment, the reflective layer 14 includes a plurality of SiO 2 films and TiO 2 films arranged alternately. In an alternative embodiment, the reflective layer 14 can be made of materials selected from a group consisting of SiO 2 , TiO 2 , Ta 2 O 5 , SiN x , TiN x and TaN x .

The first electrode 12 is made of materials selected from a group consisting of Cr, Ti, Ni, Pt, Al, Au, Ag, Cu, W and alloys thereof. The first electrode 12 includes a base 120 covering the substrate 10 and a plurality of connecting sections 122 extending upwardly from the base 120 . The base 120 can be circular, annular, strip-shaped or grid-shaped. In this embodiment, the base 120 is strip-shaped. The light emitting chip 1 defines a plurality of ion regions 13 extending upwardly from an upper surface of the base 120 to an interior of the first semiconductor layer 180 , as shown in FIG. 1 . The ion regions 13 are formed by implanting a plurality of positive ions into the reflective layer 14 , the transparent conductive layer 16 , the connecting layer 19 , and the light emitting structure 18 . Each ion region 13 defines a receiving groove 13 a therein. The receiving groove 13 a extends upwardly from the upper surface of the base 120 to an interior of the first semiconductor layer 180 via physical etching or chemical etching. The connecting sections 122 are received in the receiving grooves 13 a , respectively. The positive ions to form the ion regions 13 are selected from a group consisting of H + , He + , O + , Ar + , N + , and Ne + . The lattice defects of the ion regions 13 are increased because the implanted ions break up the lattice structure of the ion regions 13 . Thus, the ion regions 13 can function as a high resistant insulation layer to insulate the connecting section 122 from the active layer 182 , the second semiconductor layer 184 , the connecting layer 19 , the transparent conductive layer 16 , and the reflective layer 14 .

The substrate 10 is, made of electrically conductive metallic or semiconductor materials. The substrate 10 can be made of materials selected from a group consisting of Si, SiC, GaN, ZnO and Al 2 O 3 . A welding pad 15 is formed on a bottom surface of the substrate 10 , opposite to the first electrode 12 as shown in FIG. 1 . Therefore, the first semiconductor layer 180 is capable of being connected to external power source via the first electrode 12 , the substrate 10 and the welding pad 15 in order.

The light emitting structure 18 is etched to expose a part of the transparent conductive layer 16 . The second electrode 17 is formed on the exposed transparent conductive layer 16 and connected with the external power source through a metallic wire 11 . Therefore, the second semiconductor layer 184 can be connected to the external power source via the connecting layer 19 , the transparent conductive layer 16 and the second electrode 17 in order. Since the electrodes 12 , 16 are not formed on the first semiconductor layer 180 of the light emitting chip 1 , light emitting from the active layer 182 can wholly and easily travel to the external environment via an upper surface of the first semiconductor layer 180 ; accordingly, lighting extraction efficiency of the present light emitting chip 1 is high.

Referring to FIG. 2 , a light emitting chip 2 in accordance with a second embodiment of the present disclosure is provided. Different from the first embodiment, the light emitting structure 18 is etched and a part of the second semiconductor layer 184 is exposed. A through hole 184 a is defined in the second semiconductor layer 184 to extend from an exposed upper surface of the second semiconductor layer 184 via the connecting layer 19 to the transparent conductive layer 16 . The second electrode 17 is formed on the second semiconductor layer 184 and extends in the through hole 184 a to contact the transparent conductive layer 16 .

In the light emitting chip 1 , 2 described above, as shown in FIG. 1 or FIG. 2 , the first electrode 12 is buried inside the light emitting chip 1 , 2 , rather than formed on the upper surface of the first semiconductor layer 180 . Therefore, light emitting from the first semiconductor layer 180 will not be blocked by the first electrode 12 , thereby improving illuminating efficiency of the light emitting chip 1 , 2 .

Besides, the reflective layer 14 can be made of thermal conductive materials to further improve heat dissipation efficiency of the light emitting chip 1 , 2 .

It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.