DE10306311B4 - Radiation-emitting semiconductor device with diffusion stop layer - Google Patents

Abstract

Radiation-emitting semiconductor component with a layer structure, the
An n-doped cladding layer (18),
A p-doped cladding layer (20),
An active layer (14) based on InGaAlP, which is arranged between the n-doped cladding layer (18) and the p-doped cladding layer (20),
A diffusion stop layer (16) arranged between the active layer (14) and the p-doped cladding layer (20) and comprising a strained superlattice,
characterized in that
- The diffusion stop layer (16) with a dopant concentration above 0.5 × 10 ¹⁸ cm ^-3 n-doped.

Description

The The invention relates to a radiation-emitting semiconductor component with a layered structure comprising an n-doped cladding layer, a p-doped cladding layer, one between the n-doped cladding layer and the p-type cladding layer disposed active layer Base of InGaAlP, and one between the active layer and the Contains p-doped cladding layer disposed diffusion stop layer.

In the present case, the materials based on InGaAlP include all mixed crystals having a composition which falls under the formula In _x (Ga _y Al _1-x ) _1-x P with 0 ≦ x ≦ 1, 0 ≦ y ≦ 1.

LEDs based on InGaAlP by varying the Al content with emission in a wide spectral range made from red to yellowgreen become. By the change the Al content may be the bandgap of the InGaAlP system from 1.9 eV to 2.2 eV are tuned.

in the Operation of such LEDs is observed a decrease in the light output in dependence of the operating conditions. The main cause of this aging is deliberately introduced magnesium doping of the p-type cladding layer considered. there It may already be during the epitaxy process when growing a GaP window layer, which occurs at high temperatures, to a diffusion of Mg dopant atoms come along the concentration gradient towards the active layer.

Also During operation of the LEDs, aging occurs.

One Approach to countering the aging problem is diffusion the Mg dopant atoms from the p-doped cladding layer into the active layer to reduce. In order to maximize the life of the Light-emitting diodes it is desirable to prevent the magnesium diffusion as far as possible.

The publication JP 10-209 573 A describes a radiation-emitting semiconductor component according to the preamble of patent claim 1.

The publication JP 11-068 150 A describes a light-emitting element in which the cladding layers each contain a defect-rich layer, the dopants capture from the cladding layers.

The publication DE 199 57 312 A1 describes a light emitting diode having a first conductivity type light emitting layer and a second conductivity type cladding layer separated by a first conductivity type barrier interlayer.

Of the Invention is based on the object, a generic radiation-emitting Specify semiconductor device, the improved aging properties having.

These The object is achieved by a radiation-emitting semiconductor component solved with the features of claim 1. Further advantageous embodiments and further developments of the invention will become apparent from the dependent claims 2 to 10th

According to the invention, it is provided in a radiation-emitting semiconductor component of the aforementioned type that a diffusion stop layer is formed by a strained superlattice and n-doped with a dopant concentration above 0.5 × 10 ¹⁸ cm ^-3 . It has surprisingly been found that the diffusion of p-type dopant atoms is suppressed substantially more strongly by such a superlattice than in the case of conventional diffusion stop layers.

In a preferred embodiment The invention provides that the diffusion stop layer by an alternating tensil / compressively strained superlattice is formed. this leads to to a particularly efficient suppression of dopant diffusion through the stop layer.

In particular, it can advantageously be provided that the superlattice of the diffusion stop layer consists of N periods of tensilely strained In _x (Ga _y Al _1-y ) _1-x P layers (with 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) and compressively In _x (Ga _y Al _1-y ) _1-x P layers (with 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), where N is between 2 and 40, in particular between 5 and 20 and preferably between 8 and 15 lies. In a particularly preferred embodiment, N is for example equal to 10. Furthermore, the layers of the superlattice preferably have the same composition.

In an advantageous embodiment of the device according to the invention, the superlattice of the diffusion stop layer consists of In _x Al _1-x P layers (with 0 <x <1).

In In the above context, it has been found to be expedient if the Stress in the range of 0.1% to 5%, preferably in the range of 0.5% to 2%, more preferably from 0.7% to 1%.

The Invention offers particularly large Advantages when the p-doped cladding layer p-doped with magnesium is.

Both types of layers are preferred Superlattice with a dopant concentration in the range between 0.75 inclusive and including 1.5 × 10 ¹⁸ cm ^-3 provided.

there In particular, an n-doping with tellurium has been found to be advantageous exposed. The tellurium doping tip passing through the superlattice is pinned, then serves as an effective diffusion stop for the p-type dopant atoms.

In a preferred embodiment, a transparent coupling-out layer is arranged on the uppermost jacket layer of the layer structure. In particular, the transparent coupling-out layer may consist essentially of GaP. This coupling-out layer is typically epitaxially deposited using phosphine (PH ₃ ) for one to two hours at a temperature above 800 ° C. The required high temperatures favor the diffusion of dopant atoms from the p-doped cladding layer into the active layer.

The active layer may be defined, for example, by a p-n junction, be formed a quantum well or a Mehrfachquantentopf.

Further advantageous embodiments, features and details of the invention arise from the dependent ones claims, the description of the embodiment and the drawing.

The Invention will be related to an embodiment in the context closer to the drawing explained. There are only those for the understanding the invention essential elements shown. It shows

1 a schematic representation of a sectional view of a radiation-emitting semiconductor device according to an embodiment of the invention; and

2 a detail of the representation of 1 ,

1 shows a schematic representation of a sectional view of a generally with 10 designated InGaAlP LED according to an embodiment of the invention. Here are the schematic representation of the 1 only the layers essential for the understanding of the invention are shown.

It It is understood, however, that more Layer, such as buffer layers, interlayers, ramps and may also be present.

For the InGaAlP LED 10 is on a Si-doped GaAs substrate 12 a layer sequence grown on InGaAlP-based, which has an n-doped cladding layer 13 , an active layer 14 and a magnesium p-doped cladding layer 20 contains. On the p-cladding layer 20 became a GaP window layer during the epitaxy process at 840-860 ° C 22 grew up.

To the diffusion of Mg dopant atoms from the p-cladding layer 20 into the active layer 14 otherwise suppress the high growth temperatures for the GaP window layer 22 occurs between the active layer 14 and the p-type cladding layer 20 a diffusion stop layer 16 brought in. The diffusion stop layer 16 consists in the embodiment of a highly n-doped strained superlattice.

As best in the presentation of 2 to recognize, there is the superlattice of the diffusion stop layer 16 from an alternating sequence of 4 nm thick, tensely strained InAlP layers 16a and also 4 nm thick, compressively strained InAlP layers 16b , In the exemplary embodiment, the superlattice contains N = 10 such layer pairs 16a . 16b ,

The points above and below the layers in 2 indicate that the alternating sequence contains more than the six layers shown. The degree of bracing is chosen in each case in the concrete embodiment in both types of layers to 0.8%.

Both types of layers are highly n-doped with tellurium at a dopant concentration of 0.75 to 1.5 × 10 ¹⁸ cm ^-3 . The tellurium dopant tip, which is pinned by the superlattice, then acts as an effective diffusion stop for the magnesium dopant atoms from the p-type cladding layer 20 ,

In order to check the effect of the diffusion stop layer according to the invention, SIMS (Secondary Ion Mass Spectrometry) depth profiles of a light-emitting diode according to the invention 10 and a comparison light emitting diode without diffusion stop layer added. The set Mg dopant concentration of the p-cladding layer is the same in both cases and is about 5 × 10 ¹⁷ cm ^-3 .

In the comparative light-emitting diode, starting from the p-type cladding layer, there is a magnesium concentration only slightly decreasing and thus far into the light-generating layers, above 1 × 10 ¹⁷ cm ^-3 .

On the other hand, the diffusion of the Mg atoms by the introduction of the described diffusion stop layer 16 effectively stopped in this area and suppressed further penetration. In the light-emitting diode according to the invention, the Mg concentration is in the range of lichterzeu ing layers 14 below 1 × 10 ¹⁶ cm ^-3 , and thus at a value that is not critical for the aging behavior of the light-emitting diode.

Claims (10)

Radiation-emitting semiconductor component with a layer structure, comprising - an n-doped cladding layer ( 18 ), - a p-doped cladding layer ( 20 ), - one between the n-doped cladding layer ( 18 ) and the p-doped cladding layer ( 20 ) arranged active layer ( 14 ) based on InGaAlP, - one between the active layer ( 14 ) and the p-doped cladding layer ( 20 ) arranged diffusion stop layer ( 16 ), which has a strained superlattice, characterized in that - the diffusion stop layer ( 16 ) with a dopant concentration above 0.5 × 10 ¹⁸ cm ^-3 n-doped. A radiation-emitting semiconductor component according to claim 1, characterized in that the diffusion stop layer ( 16 ) has an alternating tensil / compressively strained superlattice. A radiation-emitting semiconductor component according to claim 2, characterized in that the superlattice of the diffusion stop layer ( 16 ) N periods of tensilely strained In _x (Ga _y Al _1-y ) _1-x P layers ( 16a ) with 0 ≦ x ≦ 1, 0 ≦ y ≦ 1 and compressively stressed In _x (Ga _y Al _1-y ) _1-x P layers ( 16b ) with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, where N is between 2 and 40, preferably between 5 and 20, particularly preferably between 8 and 15. A radiation-emitting semiconductor component according to claim 3, characterized in that the superlattice of the diffusion stop layer ( 16 ) consists of InAlP layers. Radiation-emitting semiconductor device according to one of the preceding claims, characterized in that the Tension in the range of 0.1% to 5%, preferably in the range of 0.5% to 2%, more preferably in the range of 0.7% to 1%. Radiation-emitting semiconductor component according to one of the preceding claims, characterized in that the p-doped cladding layer ( 20 ) is p-doped with magnesium. Radiation-emitting semiconductor component according to one of the preceding claims, characterized in that the diffusion-stop layer ( 16 ) is n-doped with tellurium. Radiation-emitting semiconductor component according to one of the preceding claims, characterized in that the n-type dopant concentration of the diffusion stop layer ( 16 ) is between 0.75 and 1.5 x 10 ¹⁸ cm ^-3 inclusive. Radiation-emitting semiconductor component according to one of the preceding claims, characterized in that on the uppermost cladding layer ( 20 ) of the layer structure has a transparent coupling-out layer ( 22 ), which preferably consists essentially of GaP. Radiation-emitting semiconductor component according to one of the preceding claims, characterized in that the active layer ( 14 ) has a pn junction, a quantum well or a multiple quantum well.