CN100418203C - Electroluminescence non-destructive testing method for light-emitting diode epitaxial wafers - Google Patents

Abstract

The present invention relates to a detection method for epitaxial wafers of light emitting diodes, which belongs to the technical field of detecting instruments. In the present invention, a positive electrode and a negative electrode are arranged on the surface of an epitaxial wafer of a light emitting diode, and a high-voltage constant current source is connected to the positive electrode and the negative electrode to break down a reverse diode composed of a p-shaped layer and an n-shaped layer in the epitaxial wafer of the light emitting diode. The whole circuit is switched on to trigger a luminous layer of the epitaxial wafer of the light emitting diode to emit light for achieving the aim of detection. The measurement method has the advantages of directness, no destruction and convenience, and in respect to photo-fluorescence, the present invention can also obtain electricity parameters of positive switching-on voltage, reverse-leakage current, etc., which are very important to LED (light emitting diode) epitaxial wafers.

Description

Electroluminescence non-destructive testing method for light-emitting diode epitaxial wafers

technical field

The invention relates to a detection method of a light-emitting diode (LED) epitaxial wafer, belonging to the field of detection instruments.

Background technique

After the incandescent lamp was invented more than 100 years ago, the cheap and efficient white light source made of red, green and blue LEDs will replace the light source invented by Edison sooner or later. Because LED has very high economic benefits, its development prospect is very broad, and it has a huge market capacity. Since lighting consumption accounts for 20% of the total power consumption, vigorously developing LED technology will be an effective way to save energy. LED will definitely be the lighting equipment of the future.

The main work for current LEDs is to reduce production costs, increase efficiency and expand the range of useful colors. In terms of production, due to the fierce competition in the LED market, the production process must attach great importance to yield and quality, so the on-line detection and quality control of LED semiconductor epitaxial wafers are very important in the production process. At present, various enterprises in our country lack the necessary testing equipment, especially the high-speed, non-destructive online testing in the production process.

At present, there are two methods for luminescence detection of LED epitaxial wafers: photoluminescence and electroluminescence. The photoluminescent detection method is to use a short-wavelength laser to irradiate the LED epitaxial wafer to detect its luminous effect. However, this is an indirect detection method that cannot directly reflect the electroluminescent effect of LED epitaxial wafers. At the same time, due to the high price of short-wavelength lasers, the detection cost of blue-green LED epitaxial wafers is very high. Electroluminescence detection is to apply a forward bias voltage on the p and n junctions of the LED epitaxial wafer to make it emit light to detect the luminous effect. The common method is to punch holes on the surface of the epitaxial wafer and connect an electrode to the p-type layer. So this detection method is destructive and not continuous.

Contents of the invention

The purpose of the present invention is to provide a non-destructive LED epitaxial wafer electroluminescent detection method. The structure of the LED epitaxial wafer (see Figure 1) is that the surface layer is a uniformly covered p-type layer, the LED light-emitting layer is underneath, and the highly conductive N-type layer is underneath, and finally a non-conductive substrate. In order to perform electroluminescent detection, two electrodes need to be placed on the surface of the epitaxial wafer, one of which is a fixed negative electrode (connected to the negative pole of the power supply); the other is a positive electrode, and a high-voltage constant current source is added between the two electrodes. Since the p-type layer on the surface of the LED epitaxial wafer is very thin and has a large resistance, most of the current will flow through the diode formed by the p-n junction. According to the characteristics of the diode, the forward diode is equivalent to conduction, and the high voltage will be mainly applied to the reversely connected diode, causing it to be broken down by the high voltage and conduct. Due to the use of a high-voltage constant current source, the current flowing through the diode can be controlled to ensure that the reverse breakdown diode will not be destroyed under the condition of being broken down. In order to complete the detection of the luminescence quality of the whole epitaxial wafer, the electroluminescence quality of the whole epitaxial wafer can be obtained by moving the positive electrode on the surface.

Therefore content of the present invention can be expressed as follows:

On the surface of the p-type layer of the light-emitting diode epitaxial wafer, two positive and negative electrodes are placed at the same time, and a high-voltage constant current source is connected to the positive and negative poles, so that the diode composed of the p-type layer and n-type layer in the light-emitting diode epitaxial wafer is Breakdown conduction, the whole circuit is turned on, and the light-emitting layer of the light-emitting diode epitaxial wafer is triggered to emit light, so as to achieve the purpose of detection. The light-emitting layer is located between the p-type layer and the n-type layer, and the negative electrode is fixed on the p-type layer. On the surface, the positive electrode can move on the surface of the p-type layer. This measurement method is direct, non-destructive, and convenient. Compared with photoluminescence, it can also obtain electrical parameters that are very important for LED epitaxial wafers, such as forward conduction voltage and reverse leakage current.

Description of drawings

Figure 1 is a schematic diagram of the LED epitaxial wafer structure and detection state.

Detailed ways

In FIG. 1, 1 is a p-type layer, 2 is an n-type layer, 3 is a light-emitting layer, and 4 is a substrate. When testing, place positive and negative electrodes on the surface of the LED epitaxial wafer and add a high-voltage constant current source. Due to the breakdown of the reverse diode, the luminous condition of the measured point can be measured. After measuring a point, move the positive electrode, and the same method as above can continue to detect, and continuously move the positive electrode to measure the luminescence status of the entire LED epitaxial wafer.

Claims (1)

1. A detection method for a light-emitting diode epitaxial wafer, which is characterized in that two positive and negative electrodes are placed on the surface of the p-type layer of the light-emitting diode epitaxial wafer, and a high-voltage constant current source is connected to the positive and negative poles, so that the light-emitting diode The diode composed of p-type layer and n-type layer in the epitaxial wafer is broken down and turned on, so that the entire circuit is turned on, causing the light-emitting layer of the light-emitting diode epitaxial wafer to emit light, so as to achieve the purpose of detection. The light-emitting layer is located in the p-type layer Between the n-type layer, the negative electrode is fixed on the surface of the p-type layer, and the positive electrode can move on the surface of the p-type layer.

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