DE102007019209A1 - Silica based light emitter, has front-lateral metallic contact, dielectric protective layer, silica substrate and rear side, conductive contact layer - Google Patents

Abstract

The silica based light emitter has a front-lateral metallic contact (6), a dielectric protective layer (4), silica substrate (1) and a rear side, conductive contact layer. A thin silica dioxide layer (3) between Silica substrate and dielectric protective layer, produced by local thermal oxidation within an environment formed by a thick Silica dioxide layer, contains europium luminescence centers (5). The electrical connections are provided at metallic contact and rear aluminum layer (8).

Description

The The invention relates to the construction of an Si-based light emitter the basis of an MIS (metal-insulator-semiconductor) structure or MIM (metal-insulator-metal) structure.

Si-based light emitter [ Rebohle, L. et al .: Blue photo- and electroluminescence of silicon dioxide layers ion-implanted with group IV elements. Appl. Phys. 71, 131-151 (2000) ] are becoming increasingly important for the integration of optical and electrical functions on a chip. Potential applications range from the development of integrated optocouplers [ DE 100 11 258.7 ] via miniaturized sensors to light emitter arrays for the fluorescence analysis of biochemical analytes [ DE 101 30 568.0 ].

Si-based Light emitters are characterized by the fact that they are compatible with the conventional ones Methods of Si technology are monolithically processed on Si can. Unlike light emitters based on Compound semiconductors need Si-based light emitters not manufactured separately and not by means of a hybrid technology consuming associated with Si-based integrated circuits.

Of the Si-based light emitters in the narrower sense consists of a MIS or MIM structure, in which under application of an electrical voltage energetic charge carriers from the metal or the semiconductor in inject the insulator. The insulator is preceded by Process steps modified so that in him or on the Interfaces to the metal or the semiconductor Lumineszenzzentren are located. The charge carriers are in the insulator under the influence of the electric field accelerates in the direction of the counter electrode and transfer part of the kinetic energy gained by impact excitation on the luminescence centers, which thereby go into an excited state. The luminescence centers then return to the ground state, emitting a photon. With the known Si-based light emitters only one color is eaten represent.

The The aforementioned mode of action differs considerably from the mode of action of light emitting diodes (LED) based on compound semiconductors or organic materials (OLED). An LED becomes charge carriers different polarity (in the first case negatively charged Electrons and positively charged holes) from both electrodes injected into the structure, and the luminescence is transmitted directly through the recombination of both types of charge carriers in the recombination zone generated. In contrast, in Si-based light emitters in the Essentially only one type of charge carrier (predominantly electrons) injected, which electrically excites the luminescence. Farther does luminescence not by charge carrier recombination, but by the optical excitation of the previously electrically excited Luminescence centers causes. A reversal of the applied voltage to the Si-based light emitter causes the same Charge carrier now injected from the counter electrode becomes. With asymmetric layer structure is with a shift to calculate the performance parameter. A possible injection of charge carriers of opposite polarity from the corresponding counter electrode with lower intensity plays for the mode of action does not matter, but it can lead to a further modification of the performance parameters.

Rare earth atoms which are introduced into dielectric layers (eg SiO ₂ , Si ₃ N ₄ , SiO _x N _y ) show in such MOSLEDs (LEDs based on a metal-oxide (or insulator) semiconductor device) efficient electroluminescence for the ultraviolet to infrared wavelength range. Infrared, green, blue and ultraviolet luminescence have already been used with the erbium elements Sun, JM et al .: On the mechanism of electroluminescence excitation in Er-doped SiO2 containing silicon nanoclusters. Optical Materials 27, 1050-1054 (2005) .], Terbium [ Sun, JM et al.: Bright green electroluminescence from Tb3 + in silicon metal-oxide-semiconductor devices. J. Appl. Phys. 97, 123513 (2005) ], Cerium Sun, JM et al .: lncrease of blue electroluminescence from Cedoped SiO2 layers through sensitization by Gd3 + ions. Appl. Phys. Lett. 89, 091908 (2006) ] and gadolinium [ Sun, JM et al .: Efficient ultraviolet electroluminescence from a Gd-implanted silicon metal-oxide-semiconductor device. Appl. Phys. Lett. 85, 3387-3389 (2004) ] demonstrated. Only for GaN, a switchable two-color device was reported on the basis of pn diodes, but this requires two different rare-earth atoms [ Lee DS et al .: Voltage-controlled yellow or orange emission from GaN codoped with Er and Eu. Appl. Phys. Lett. 76, 1525-1527 (2000) ] and [ Heikenfeld, J. u. Plug, AJ: Rare-earth-doped GaN switchable color electroluminescent devices. IEEE Trans. Electron Dev. 49, 1545-1551 (2002) ].

Of the Invention is based on the object, a multicolor emitting Si-based light emitter to realize the simple design and can be produced with only one rare earth doping.

The The object is achieved by the in the claim solved characteristics.

The doping of the dielectric layer is carried out with europium. This doping of the dielectric layer leads to electrical operation of the MOSLED, depending on the level of current injection predominantly red or predominantly blue electroluminescence. Europium has the special property of forming two different oxidation states, which can lead to two different optical transitions, depending on the excitation by energetic electrons of different energies. The Eu ³⁺ state allowed 4f ⁵ D ₀ - ^7. F _J (J = 1, 2, 3) intra-shell transition, leading to luminescence in the red region (major band at 616 nm), while the Eu ²⁺ - State for blue emission occurs via two efficient bands at 400 and 470 nm. The latter is explained by a strong interaction of 5d electrons with the crystal field of the matrix and is based on 4f ⁶ 5d - 4f ⁷ ( ⁸ S _7/2 ) junctions.

With The invention can therefore the emission of light different Wavelength can be realized.

The Invention will be described below by way of example for a MOSLED structure explained in more detail.

In show the accompanying drawing

1 an MIS structure according to the invention with a dielectric layer containing the europium atoms,

2 the electroluminescence spectra of the SiO ₂ : Eu-MOSLED devices with different Eu concentrations,

3 the electroluminescence intensity of a MOSLED device,

4 shows the color-related brightness differences of corresponding MOSLEDs at different excitation currents.

The MOSLED device according to 1 consists of a Si substrate 1 on which in a field oxide environment 2 a thin SiO ₂ layer 3 (Thickness 100 nm) is arranged. This SiO ₂ layer 3 contains Eu ⁺ atoms with peak concentrations of 0.5 ... 3 at%, which were introduced by ion implantation and subsequent annealing and the corresponding luminescence centers 5 in the thin silicon dioxide layer 3 form. On top of this is a SiON layer (50 nm) produced by PECVD (plasma-enhanced chemical vapor deposition) as a dielectric protective layer 4 , On it is indium tin oxide (ITO) as a transparent metal contact 6 with a thickness of 100 nm. The electrical contacting takes place via a to the metal contact 6 connected ITO interconnect 7 and on the back of the wafer via a correspondingly applied aluminum layer 8th ,

2 shows the electroluminescence as a function of the wavelength of the SiO ₂ : Eu-MOSLED devices for different Eu concentrations. The excitation current is 10 μA, with the voltage of negative polarity at the interconnect 7 , with positive polarity corresponding to the aluminum layer 8th is applied as an electrode. The diameter of the active area is 200 μm. The predominantly red luminescence is the peak in the range 600-650 nm wavelength, which predominantly blue the emission in the range 400-500 nm assign.

The electroluminescence intensity according to 3 was realized with MOSLED's containing 0.5% Eu, measured at 400 nm (solid) and 616 nm (dashed) as a function of excitation current (left scale). The right-sided arrow shows the applied voltage as a function of the excitation current (right scale). The inserted graph shows the ratio of blue to red electroluminescence as a function of the excitation current. The diameter of the active area is 200 μm. The red emission dominates for the injection current range 2 × 10 ^-8 -1 × 10 ^-4 A, while the blue emission dominates in the range 1 × 10 ^-4 -1 × 10 ^-3 A. The inserted graph shows the ratio of blue to red electroluminescence as a function of the excitation current. In 4 it is clear that switching between the dominant colors blue (b) and red (a) is possible by suitable choice of the operating current range, and also intermediate shades such. B. violet or purple (c) can be realized depending on the injected current density. This is done by the in 4 visible different shades of gray at different current densities.

1

Si substrate (Semiconductor)

2

Feldoxidumgebung

3

thin SiO ₂ layer (insulator)

4

dielectric protective layer

5

Europium luminescence

6

metal contact

7

interconnect

8th

aluminum layer

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10011258 [0002]
• - DE 10130568 [0002]

Cited non-patent literature

• - Rebohle, L. et al .: Blue photo- and electroluminescence of silicon dioxide layers ion-implanted with group IV elements. Appl. Phys. 71, 131-151 (2000) [0002]
• - Sun, JM et al .: On the mechanism of electroluminescence excitation in Er-doped SiO2 containing silicon nanoclusters. Optical Materials 27, 1050-1054 (2005) [0006]
• - Sun, JM et al.: Bright green electroluminescence from Tb3 + in silicon metal-oxide-semiconductor devices. J. Appl. Phys. 97, 123513 (2005) [0006]
• - Sun, JM et al .: lncrease of blue electroluminescence from Cedoped SiO2 layers through sensitization by Gd3 + ions. Appl. Phys. Lett. 89, 091908 (2006) [0006]
• - Sun, JM et al .: Efficient ultraviolet electroluminescence from a Gd-implanted silicon metal-oxide-semiconductor device. Appl. Phys. Lett. 85, 3387-3389 (2004) [0006]
• - Lee DS et al.: Voltage-controlled yellow or orange emission from GaN codoped with Er and Eu. Appl. Phys. Lett. 76, 1525-1527 (2000) [0006]
• - Heikenfeld, J. u. Plug, AJ: Rare-earth-doped GaN switchable color electroluminescent devices. IEEE Trans. Electron Dev. 49, 1545-1551 (2002) [0006]

Claims (1)

Si-based light emitter, consisting of a front metal contact, a dielectric protective layer, a Si substrate and a rear, conductive contact layer, characterized in that between Si substrate ( 1 ) and dielectric protective layer ( 4 ) within a thin SiO ₂ layer ( 3 ) produced by local thermal oxidation within an environment formed by a thicker SiO ₂ layer, europium luminescent centers ( 5 ) and that electrical connections to metal contact ( 6 ) and back aluminum layer ( 8th ) are provided, which are connected to a current source for application to a variable, for a selectable time constant current.