DE102007057672A1 - Optoelectronic semiconductor body e.g. thin film-LED chip, for use in headlight i.e. motor vehicle headlight, has Schottky contact formed between extension and n-type layer and operated in reverse direction during operation of active layer - Google Patents

Abstract

The body has an epitaxic semiconductor layer sequence with an active layer (4) producing and/or receiving electromagnetic radiation. The sequence has aluminum indium gallium nitride and n-type layers (1, 5), where the layer (4) is arranged between the n-type layers. An electrical contact layer (7) is arranged in the layer (5). An extension (70) of the contact layer extends to the layer (1) through a gap (40) of the layer (4). A Schottky contact (9) is formed between the extension and the layer (1) and operated in a reverse direction during operation of the layer (4) in a flow direction.

Description

The The present application relates to an optoelectronic semiconductor body.

It is an object of the present application, an optoelectronic Specify semiconductor body in which the risk of damage by Electrostatic discharge (ESD, electrostatic discharge) especially is low and has a high efficiency.

These The object is achieved by an optoelectronic semiconductor body solved according to claim 1. advantageous Embodiments and developments are in the dependent Claims specified. The disclosure of the claims is hereby explicitly by reference to the description added.

It is an optoelectronic semiconductor body with a epitaxial semiconductor layer sequence specified. The epitaxial Semiconductor layer sequence contains an active layer, which for generating and / or receiving electromagnetic radiation is provided. In particular, it is the optoelectronic Semiconductor body to a LED chip, a laser diode chip and / or a photodiode chip.

The Epitaxial semiconductor layer sequence contains a first n-type layer and a second n-type layer, between where the active layer is arranged. Conveniently, contains the epitaxial semiconductor layer sequence between the rule first n-type layer and the active layer a p-type Layer.

at an expedient embodiment, the optoelectronic Semiconductor body a tunnel junction between the first n-type layer and the active layer, in particular between the first n-type layer and the p-type layer.

Of the Tunnel junction contains at least one n-type Tunnel junction layer, that of the first n-type layer facing, and a p-type tunnel junction layer, which faces the active layer. The p-type tunnel junction layer may be included in the p-type layer which may be n-type tunnel junction layer be contained in the first n-type layer.

Between the n-type and p-type tunnel junction layers In an embodiment, an intermediate layer is arranged. The n-type and / or p-type tunnel junction layer in another development as a superlattice of alternating Layer pairs configured. The intermediate layer preferably has a plurality of layers of different material composition on. For example, the optoelectronic semiconductor body is based on the semiconductor material AlInGaN and the intermediate layer has at least two layers with different aluminum content on.

Of the Optoelectronic semiconductor body has an electrical Terminal layer disposed on the second n-type layer is and in particular comprises a metallic material or from it consists. Conveniently, the electrical Connection layer on the side facing away from the active layer side arranged the second n-type layer.

One Elbows of the electrical connection layer extends through a breakthrough of the active layer to the first n-type layer. The spur of the electrical connection layer So runs in particular in the direction of the second n-type layer to the first n-type layer through the second N-type layer through, through the active layer and in particular through the p-type layer to the first n-type layer. Preferably, the tail extends in this direction also facing through one of the active layer Edge region of the first n-type layer, up to a Middle region of the first n-type layer, which is the edge region in the direction away from the active layer.

Between the tail of the electrical connection layer and the first n-type layer, in particular the central region of the first n-type layer, a protection diode is formed. At the protection diode it is, for example, a pn junction or to a Schottky contact, also Schottky barrier or Schottky diode called. In particular, in an embodiment in which the protective diode is a Schottky-Konakt, it is preferably from a sub-area of the foothill and a sub-area of the first n-type Shift - for example, from a subarea of the mid-range the first n-type layer - formed. The subfields of the Foothills and the first n-type layer, which the Form Schottky contact, expediently border to each other.

In particular, the tail of the electrical connection layer establishes an electrically conductive connection between the protective diode and the region of the electrical connection layer arranged on the second n-conductive layer. It can be formed in one piece or in several parts. In one embodiment, the tail or at least a portion of the tail and on the second n-lei The layer of the electrical connection layer arranged the same material. It is also conceivable that the region of the electrical connection layer and the extensions arranged on the second n-type layer have different materials.

advantageously, During operation of the active layer in the forward direction of the protective diode operated in the reverse direction. In this way is with advantage the Risk of damage to the optoelectronic semiconductor body reduced by electrostatic discharge.

at the same time can be a particularly compact design of the semiconductor body be achieved. In particular, the space requirement for the Protective diode used as protection against electrostatic discharge (ESD) especially low. The radiation-emitting surface of Optoelectronic semiconductor body is therefore, for example in comparison to an ESD protection diode arranged laterally next to the active layer, extraordinary big.

at In one embodiment, the semiconductor body has another electrical connection layer on top of the first n-type Layer is arranged. In particular, it is on the of the active Layer facing away from the first n-type layer, and thus on one of the electrical connection layer opposite Side, arranged. The wei tere electrical connection layer has preferably a metallic material or consists thereof.

at an advantageous development is the first n-type layer only in places from the further electrical connection layer covered. For example, the further electrical connection layer represents a bond pad. In this embodiment, the coupling takes place the electromagnetic radiation generated by the active layer and / or the coupling of the to be received by the active layer Radiation partially or completely through the first n-type Layer through.

at In a continuing education overlap the foothills of the electrical connection layer, which is characterized by the breakthrough of extending active layer to the first n-type layer, and the further electrical connection layer laterally to each other. For example is the extension of the electrical connection layer in Top view of the first n-type layer partially or completely arranged under the further electrical connection layer.

at This development is advantageously in the field in which the further electrical connection layer and the tail overlap the electrical connection layer, from the active layer no electromagnetic radiation generated. For radiation in one of the further electrical connection layer covered area the active layer is generated, there is a risk that they are from the further electrical connection layer is absorbed, what unfavorable to the efficiency of the semiconductor body effect. Analog stands at a radiation-receiving semiconductor body the area covered by the first terminal layer of the active layer not to receive electromagnetic radiation to disposal.

In an advantageous embodiment of the semiconductor body, the first n-type layer has at least one n-doped region and nominally undoped region. A "nominally undoped region" is understood to mean an undoped or slightly n-doped region. "Low n-doped" in the present context means that the concentration of an n-dopant is at most 0.1 times, preferably at most 0.05 times is so large and in particular at most 0.01 times as large as the concentration of an n-type dopant in the n-doped region. For example, the concentration of the n-type impurity in the nominally undoped region is less than or equal to 1 × 10 ¹⁸ 1 / cm ³ , preferably less than or equal to 5 × 10 ¹⁷ 1 / cm ³ , more preferably less than or equal to 1 × 10 ¹⁷ 1 / cm ³ .

at An advantageous development of this embodiment is the protective diode a Schottky contact that is between the low n-doped or undoped Area and the tail of the second electrical connection layer educated. In this way, a wide depletion zone of the Schottky contact.

at In another development, the first n-doped layer has a first n-doped area, the nominal undoped area and a second n-doped region extending in the direction of the active Layer away in this order. Especially the first n-doped region is that of the active layer facing edge region through which the tail of the electrical connection layer extends through, and at the no minell undoped region around the central region of the first n-doped layer. The tail ends so in particular in the nominal undoped Layer.

at another development has the tail of the electrical Terminal layer adjacent to the first n-type layer Edge piece on, which is a metal with a high work function having. A "high" work function has one in particular Value of greater than or equal to 3.5 eV, preferably from greater than or equal to 4.0 eV, for example, greater or equal to 4.5 eV. For example, the edge piece Platinum and / or palladium on.

at In another embodiment, the optoelectronic semiconductor body between the second n-type layer and the electrical connection layer a dielectric layer having at least one opening contains.

at an expedient embodiment is adjacent to the electrical Connection layer in the region of the at least one opening to the second n-type layer. In other words, that is epitaxial semiconductor layer sequence through the at least one opening the dielectric layer through the electrical connection layer electrically contacted. Between the second n-type layer and the electrical connection layer is preferably an ohmic Contact trained. A total area of the opening or the openings - especially exclusively one laterally overlapping with the breakthrough of the active layer Area - is in an advantageous embodiment maximum 10%, in an advantageous variant a maximum of 5% of the base area the epitaxial semiconductor layer sequence. Indicates the dielectric layer several openings is at a lateral distance between two openings, for example 20-30 μm.

The Dielectric layer preferably has a refractive index, the is less than the refractive index of the second n-type layer. The refractive index of the dielectric layer differs, for example by 1 or more of the refractive index of the second n-type layer from. Preferably, the dielectric layer has a translucent or transparent material.

When Materials for the dielectric layer are in particular Silicon dioxide, silicon nitride and spin-on glass into consideration. Further transparent, in a variant porous, dielectric materials whose Refractive index is less than 1.5, are also suitable. Advantageous are transparent porous materials whose refractive index is approximately equal to that of the air.

through the dielectric layer and / or the electrical connection layer In an advantageous embodiment, at least part of the from the active layer toward the second electrical connection layer emitted or, in the case of a radiation reception active layer, in the direction of the second electrical connection layer transmitted electromagnetic radiation in the direction of the first n-conductive layer reflected back.

By the back reflection of part of the active layer emitted toward the second n-type layer or transmitted radiation can be a particularly high efficiency of the optoelectronic Semiconductor body can be achieved.

For example in a dielectric layer whose refractive index is smaller as the refractive index of the second n-type layer, the Back reflection by total reflection done.

The dielectric layer has - for example, due to the change the refractive index - a particularly high reflection coefficient on, allowing them from the active layer toward the dielectric Layer emitted electromagnetic radiation advantageously particularly efficient in the direction of the first n-type layer back reflected. At the same time, the dielectric layer is particularly resistant to aging, so the risk of a decrease in reflectivity with the time, for example, compared to a silver layer as Reflector, only small. In addition, with advantage by means of especially at a dielectric layer having a plurality of openings, the operating current particularly homogeneous in the semiconductor layer sequence imprinted.

at an advantageous development, the dielectric layer a layer sequence of layers with alternating large and small refractive index. It puts, in other words, a distributed Bragg reflector (DBR) represents.

The electrical connection layer has in a development - at least in an edge region adjacent to the dielectric layer - a metal with a high reflection coefficient. So can with advantage the proportion of electromagnetic reflected back Radiation can be further increased. Together with the dielectric Layer is in particular the realization of an Ag-free mirror layer possible. For example, the electrical connection layer contains Al, Rh and / or Rt. Thus, a high moisture stability and / or long-term stability of the semiconductor body be achieved.

at In an advantageous embodiment, the dielectric extends Layer through the breakthrough of the active layer through to the first n-type layer and in particular by the edge region through the first n-type layer. Isolated in this way they in the breakthrough the foothills of the electrical connection layer, which also extends through the active layer so that the risk of a short circuit of the active layer through the spur is reduced.

at an advantageous embodiment, it is in the optoelectronic Semiconductor body to a thin-film LED chip.

• – an einer zu einem Trägerelement hingewandten Hauptfläche der epitaktischen Halbleiterschichtenfolge ist eine reflektierende Schicht aufgebracht oder ausgebildet, insbesondere die elektrische Anschlussschicht und gegebenenfalls die dielektrische Schicht, die zumindest einen Teil der in der Halbleiterschichtenfolge erzeugten elektromagnetischen Strahlung in diese zurückreflektiert;
• – der Dünnfilm-Leuchtdiodenchip weist ein Trägerelement auf, bei dem es sich nicht um das Wachstumssubstrat handelt, auf dem die Halbleiterschichtenfolge epitaktisch gewachsen wurde, sondern um ein separates Trägerelement, das nachträglich an der Halbleiterschichtenfolge befestigt wurde;
• – die Halbleiterschichtenfolge weist eine Dicke im Bereich von 20 μm oder weniger, insbesondere im Bereich von 10 μm oder weniger auf;
• – die Halbleiterschichtenfolge ist frei von einem Aufwachssubstrat. Vorliegend bedeutet „frei von einem Aufwachssubstrat, dass ein gegebenenfalls zum Aufwachsen benutztes Aufwachssubstrat von der Halbleiterschichtenfolge entfernt oder zumindest stark gedünnt ist. Insbesondere ist es derart gedünnt, dass es für sich oder zusammen mit der epitaktischen Halbleiterschichtenfolge alleine nicht freitragend ist. Der verbleibende Rest des stark gedünnten Aufwachssubstrats ist insbesondere als solches für die Funktion eines Aufwachssubstrates ungeeignet; und
• – die Halbleiterschichtenfolge enthält mindestens eine Halbleiterschicht mit zumindest einer Fläche, die eine Durchmischungsstruktur aufweist, die im Idealfall zu einer annähernd ergodischen Verteilung des Lichtes in der Halbleiterschichtenfolge führt, das heißt, sie weist ein möglichst ergodisch stochastisches Streuverhalten auf.

A thin-film light-emitting diode chip is characterized by at least one of the following characteristic features:

• A reflective layer is applied or formed on a major surface of the epitaxial semiconductor layer sequence facing a carrier element, in particular the electrical connection layer and optionally the dielectric layer, which reflects back at least part of the electromagnetic radiation generated in the semiconductor layer sequence;
• The thin-film light-emitting diode chip has a carrier element, which is not the growth substrate on which the semiconductor layer sequence has been epitaxially grown, but a separate carrier element which has subsequently been attached to the semiconductor layer sequence;
• The semiconductor layer sequence has a thickness in the range of 20 μm or less, in particular in the range of 10 μm or less;
• - The semiconductor layer sequence is free of a growth substrate. In the present context, "free from a growth substrate means that a growth substrate which may be used for growth is removed from the semiconductor layer sequence or at least heavily thinned. In particular, it is thinned such that it alone or together with the epitaxial semiconductor layer sequence is not self-supporting. The remainder of the highly thinned growth substrate is in particular unsuitable as such for the function of a growth substrate; and
• - The semiconductor layer sequence contains at least one semiconductor layer having at least one surface having a mixing structure, which leads in the ideal case to an approximately ergodic distribution of light in the semiconductor layer sequence, that is, it has the most ergodisch stochastic scattering behavior.

A basic principle of a thin-film light-emitting diode chip is, for example, in the document I. Schnitzer et al., Appl. Phys. Lett. 63 (16) 18 October 1993, pages 2174-2176 described, the disclosure of which is hereby incorporated by reference. Examples of thin-film light-emitting diode chips are in the documents EP 0905797 A2 and WO 02/13281 A1 described, whose disclosure content is hereby also included by reference.

One Thin-film LED chip is in good approximation a Lambert surface radiator and is suitable from therefore, for example, good for use in a headlamp, such as a motor vehicle headlight.

Further advantages and advantageous embodiments and further developments will become apparent from the following in connection with the 1 illustrated embodiment.

1 shows a schematic cross section through an optoelectronic semiconductor body according to an embodiment.

The Figure is not to be considered to scale. Rather, individual elements, for. B. layers, for better understanding and / or for better presentation exaggerated big, about exaggeratedly thick, to be represented.

The optoelectronic semiconductor body has a first n-conductive layer in the direction from a front side to a rear side opposite the front side 1 , a tunnel crossing 2 , a p-type layer 3 , an active layer 4 and a second n-type layer 5 on.

The epitaxial semiconductor layer sequence is based, for example, on the semiconductor material AlInGaN. In the present context, the expression "based on the semiconductor material AlInGaN" is understood to mean that the semiconductor layer sequence or at least a part thereof, particularly preferably at least the active layer, has or consists of Al _n In _m Ga _1-nm N, where 0 ≦ n ≦ 1, 0 ≤ m ≤ 1 and n + m ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it may, for example, have one or more dopants and additional constituents. For the sake of simplicity, however, the above formula contains only the essential constituents of the crystal lattice (Al, In, Ga, N), even if these can be partially replaced and / or supplemented by small amounts of further substances.

The active layer 4 is provided in this case for the emission of electromagnetic radiation. In particular, it has a pn junction, a double heterostructure, a single quantum well structure or a multiple quantum well structure for generating radiation. The term "quantum well structure" has no significance with regard to the dimensionality of the quantization, which may be quantum dots, quantum wires or at least one quantum film.

The tunnel crossing 2 In the present case, a heavily n-doped n-type tunnel junction layer, a heavily p-doped p-type tunnel junction layer and an undoped or - in particular doped with Mg as p-type dopant - intermediate layer between them. The n-type tunnel junction layer and / or the p-type tunnel junction layer may be formed as superlattices of alternating layers.

One of the active layer 4 opposite main surface 100 the first n-type layer 1 , so the front main surface, is with Auskoppelstrukturen 110 provided for light scattering. example wise, the coupling-out structures 110 in the first n-type layer 1 be self-trained. Alternatively, they can also be applied as a separate layer on these. The separate layer may be z. Example, a photonic crystal, a photonic quasi-crystal or a non-periodic coupling-out structure.

In one embodiment, the front-side main surface 100 the first n-type layer 1 with coupling-out structures 110 structured, which have a height between 100 and 1000 nm, preferably between 150 and 500 nm, and have a lateral extension between 50 and 800 nm, preferably between 80 and 500 nm. For example, the cross section of the coupling-out structures 110 an elliptical, circular, rectangular or square contour.

On the back main surface 500 the second n-type layer 5 is a dielectric layer 6 applied. In the dielectric layer 6 it may be, for example, a SiO ₂ layer. Preferably, the dielectric layer is 6 formed as a layer sequence of dielectric layers with alternating high and low refractive index, so that it represents a distributed Bragg reflector. For example, it contains a layer sequence of pairs of alternating SiO ₂ and TiO ₂ layers. In this way, a particularly high proportion of the active layer 4 Electromagnetic radiation emitted in the rear direction in the direction of the front-side main surface 100 reflected back.

The first n-type layer has two n-type regions 11 . 13 on, for example, doped with Si as n-dopant. A nominally undoped area 12 follows the first n-doped region 11 in the direction of the frontal main surface 100 to the active layer 4 and goes to the second n-doped region 13 ahead.

The dielectric layer 6 contains openings 60 in which the second n-type layer of the dielectric layer 6 is uncovered.

The dielectric layer 6 extends in the direction of the second n-type layer 5 to the first n-type layer 1 , ie in the direction from the back to the front, through a breakthrough 40 the active layer 4 ,

In other words, a recess is formed in the epitaxial semiconductor layer sequence, in particular in the form of a blind hole. The recess extends through the second n-conductive layer 5 , the active layer 4 , the p-type layer 3 and the tunnel crossing 2 through to the first n-type layer 1 , In the present case, it also passes through the second n-doped region 13 the first n-type layer 1 through to the nominal undoped area 12 ,

The side wall or the side walls of the recess are expediently of the dielectric layer 6 covered.

An electrical connection layer 7 is on the dielectric layer 6 educated. It has in the present case aluminum or consists of it. The electrical connection layer 7 extends through the openings 60 through to the second n-type layer 5 , This way is the active layer 4 electrically connected at the back.

An offshoot 70 the electrical connection layer 7 extends through the breakthrough 40 the active layer 4 through the recess to the nominal undoped area 12 the first n-type layer 1 , By means of the side wall or the side walls of the recess covering the dielectric layer 6 that the foothills 70 encloses laterally, the risk of short circuit of the active layer 4 through the foothills 70 the electrical connection layer 7 reduced.

One of the first n-type layer 1 adjacent edge piece 710 of the foothill 70 the electrical connection layer 7 has a metal with a high work function - in this case Pt - on. Between this front edge piece 710 and the nominal undoped area 12 the first n-type layer 1 is a Schottky contact 9 formed, which is a protective diode.

Alternatively, it is also conceivable that between the spur 70 and the first n-type layer 1 a pn junction is formed as a protective diode, for example by means of a p-type layer in the recess between the spur 70 and the n-type layer 1 ,

The forward direction of the Schottky contact 9 and the active layer 4 are polar oppositely. Connected to the electrical connection layer 7 and the further electrical connection layer 8th applied a voltage such that the active layer is operated in the forward direction, closes the Schottky contact 9 so that the risk of leakage through leakage is low. Applying a voltage in the reverse direction may cause a current through the Schottky contact 9 flow, so that the risk of damage to the active layer is advantageously reduced.

The frontal main surface 100 The first n-type layer is in places of another electrical connection layer 8th covered. In the present case, it is in the further electrical connection layer 8th around a metal bonding pad, which is a central area of the front-side main surface 100 the first n-type layer 1 covered. Expediently, these are / are those of the further electrical connection layer 8th Covered area (s) not roughened or structured.

In plan view of the front side main surface 100 overlap with each other through the breakthrough 40 extending spurs 70 the electrical connection layer 7 and the further electrical connection layer 8th , In particular, the lateral extent of the tail is 70 and the further electrical connection layer 8th about the same size. In this way, advantageously below the bondpad 8th from the active layer 4 no radiation generated.

The Invention is not by the description with reference to the embodiment limited to this. Rather, it encompasses every new one Characteristic as well as the combination of features, even if this feature or this combination of features in the embodiment or is not explicitly indicated in the claims.

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

• EP 0905797 A2 [0036]
• WO 02/13281 A1 [0036]

Cited non-patent literature

• I. Schnitzer et al., Appl. Phys. Lett. 63 (16) 18 October 1993, pages 2174-2176 [0036]

Claims (15)

Optoelectronic semiconductor body with an epitaxial semiconductor layer sequence that has an active Layer containing which for generating and / or for receiving electromagnetic radiation is provided, wherein the epitaxial Semiconductor layer sequence, a first n-type layer and a contains second n-type layer, between which the active layer is arranged, an electrical connection layer on the second n-type layer is arranged, a spur the electrical connection layer through a breakthrough of active Layer extends to the first n-type layer, and between the tail of the electrical connection layer and the first n-type layer, a protection diode is formed. Optoelectronic semiconductor body according to claim 1, in which the protective diode is a Schottky contact. Optoelectronic semiconductor body according to claim 1 or 2, with another electrical connection layer, the on one of the electrical connection layer opposite Side of the first n-type layer is disposed, wherein the further electrical Terminal layer and the tail of the electrical connection layer overlap laterally. Optoelectronic semiconductor body according to a of the preceding claims, wherein the first n-type Layer at least one n-doped region and a nominal has undoped area and the protective diode between the spur the electrical connection layer and the low n-doped or undoped area is formed. Optoelectronic semiconductor body according to claim 4, in which the first n-doped layer has a first n-doped layer Range, the nominal undoped area and a second n-doped area Area which faces away from each other in the direction of the active layer consequences. Optoelectronic semiconductor body according to a of the preceding claims, wherein the tail the electrical connection layer one of the first n-type layer having adjacent edge piece, which is a metal with a having high work function. Optoelectronic semiconductor body according to claim 6, wherein the edge piece has Pt and / or Pd. Optoelectronic semiconductor body according to a of the preceding claims, between the second n-type layer and the electrical connection layer, a dielectric Layer having at least one opening and the electrical connection layer in the region of the opening to the second n-type layer borders. Optoelectronic semiconductor body according to claim 8, in which the dielectric layer through the breakthrough of the extending active layer to the first n-type layer. Optoelectronic semiconductor body according to a of claims 8 or 9, wherein the dielectric layer and / or the electrical connection layer at least part of the emitted active layer or in the direction of the electrical connection layer transmitted electromagnetic radiation in the direction of the first n-conductive layer reflected back. Optoelectronic semiconductor body according to claim 10, in which the dielectric layer is a layer sequence of layers having alternating large and small refractive indices. Optoelectronic semiconductor body according to a of the preceding claims, which is a tunnel junction between the first n-type layer and the active layer having. Optoelectronic semiconductor body according to a of the preceding claims, wherein one of the active Layer facing away from the main surface of the first n-type layer roughened and / or structured. Optoelectronic semiconductor body according to a of the preceding claims, free from a growth substrate is. Optoelectronic semiconductor body according to a of the preceding claims, wherein the epitaxial Semiconductor layer sequence AlInGaN has.