JPS61247083A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To make it possible to accurately measure the foward direction voltage for obtaining the temperature of an element and to obtain an accurate thermal resistance by a method wherein a diode section where direct and weak current is to be made to flow is formed on a section where the temperature rise is measured separately from the light-emitting region to measure the temperature with direct current. CONSTITUTION:An electrically insulated layer 9 is partially formed from the surface of the P side to the substrate with chemical etching method to form an electrically independent diode B within the same element other than a diode A where the light-emitting section directly below a Zn diffusion layer 6. Therefore, it is possible to accurately measure the forward direction voltage by feeding a weak current with direct current for measuring the temperature of an element to the diode B while feeding a normal driving current to the diode A. Moreover, it is not required to change current from the large current for increase the temperature of the element to the small current for measuring the temperature of the element, thereby simplifying the measuring circuit and providing a low-price thermal resistance measuring instrument.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to improvements in semiconductor lasers.More specifically, it relates to improvements in adding a function to directly measure thermal resistance to semiconductor laser elements. It is.

[Conventional technology] Semiconductor lasers are key devices in optical fiber communications.

Therefore, the reliability of the optical fiber communication system in general is strongly influenced by the reliability of the semiconductor laser. Incidentally, the reliability of a semiconductor laser, like other semiconductor devices, depends on the element temperature, so it is necessary to accurately determine the element temperature during use. For this purpose, it is necessary to accurately measure the thermal resistance of the element.

A common method for measuring the thermal resistance of a semiconductor laser is to use the temperature dependence of the forward characteristics of a diode.

This method measures as follows. First, the forward voltage VFI is measured at room temperature T with no current flowing and at a current IFI at a level so low that the temperature rise can be ignored. Next, after flowing a sufficiently large current IFZ to raise the element temperature, the current is switched to a low level current IFI again, and the forward voltage vFl at this time is measured.

The time to switch the current from IF2 to IFI is faster than the heat of the element. yp lh t flow i' 11p
The voltage in the 3111 direction at the element temperature T' at 2 is obtained.

Therefore, the thermal resistance th can be obtained from the following formula.

R1h=(element temperature rise)/(power consumption)"(T'
-T ) / (IF2XVF2) = (Bow・-VF・)
)/(IP・・■、・)・・・・(1゜α Here, α is the temperature coefficient of the forward voltage at low level IFI and is a constant. VF2t: is the current IF2
This is the forward voltage when .

By the way, in order to obtain a more accurate thermal resistance using this method, it is necessary to make the time for switching from the current k IP2 to IFI smaller than the thermal time constant of the element.

[Problem that the invention seeks to solve]

Generally, the thermal time constant of a semiconductor laser element is several hundreds of nanoseconds.
Very small, less than t. Therefore, using the method described above, the current is
After switching from P2 to IFI, it is very difficult to accurately measure the forward voltage VFI within the thermal time constant of the element.

Particularly in semiconductor lasers, if the current IF2 is too large, the optical power within the optical element will become excessive, destroying the reflective end facets.
Laser oscillation will no longer occur. Therefore, since IP2 cannot be increased, the voltage difference (VF-VFI) becomes a small value, and unless vF can be measured more accurately than a general diode, an accurate thermal resistance value cannot be obtained.

Therefore, thermal resistance, which is an important parameter for estimating the reliability of semiconductor lasers, could not be measured with high precision.

The present invention improves these drawbacks and provides a semiconductor laser whose thermal resistance can be accurately measured.

[Means for solving problems]

The reason why the current is switched in order to measure thermal resistance in the conventional technology is that the same diode is used in the part that flows the large current IF2 to raise the temperature of the element and the part that flows the small current Iplt and measures the element temperature. .

In the semiconductor laser device of the present invention, a diode portion that is electrically insulated from a diode portion that raises the temperature of the device including a light emitting region is formed in the same device, and a diode portion that flows a small current for measuring the temperature rise of the device. There is.

Therefore, a small direct current IPI k can be passed through the portion where the temperature rise is measured independently of the light emitting region.

Since the measurement is performed using direct current, the forward voltage "F1't" for determining the element temperature III T' t can be measured with high accuracy, and therefore it is possible to determine the accurate thermal resistance.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention applied to an iZnZn diffused planar striped conductor laser.

In FIG. 1, 1 is an n-type substrate, 2 and 4 are n-type and p-type cladding layers, 3 is an active layer, 5 is an n-type cap layer, 6 and 6' are Zn diffusion layers, and 7 and 7'.

8 each has ohmic contact skin.

The above parts 1 to 8 are the same as those of a conventional semiconductor laser.

In the semiconductor laser of the present invention, an electrical isolation*/ii9 is formed, and a diode A including a light emitting portion and an electrically independent diode B are formed in the same element.

The electrically insulating layer 9 is easily formed by proton irradiation in a typical AtGaAs semiconductor laser.

Furthermore, as shown in FIG. 2, two diode portions A are formed in the same element by partially etching from the P-side surface to the substrate using chemical etching.

Bi shadow can be formed.

In the semiconductor laser according to the present invention, in addition to a diode A including a light emitting portion directly under the Zn diffusion layer 6, an electrically independent diode B is formed in the same element.

Therefore, while a normal operating current is passed through the diode A side, a small current IFI for measuring the element temperature can be passed through the diode B as a direct current, and No. 1 can be measured with high accuracy.

〔Effect of the invention〕

As explained above, in order to measure the thermal resistance of conventional semiconductor lasers, a method was used in which the large current used to increase the element temperature was switched to a small current used to measure the element temperature. Moreover, because a current switching circuit and the like are required, the thermal resistance measuring device is complicated and expensive.

Since the semiconductor laser of the present invention includes a diode with an electrically separated light emitting part and a diode for measuring thermal resistance in the same element, it is only necessary to measure with direct current, which dramatically improves the measurement accuracy of thermal resistance. effective. Additionally, because it is a direct current measurement, the measurement circuit is simple and the thermal resistance measuring device is inexpensive.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a semiconductor laser device according to the invention, and FIG. 2 is a sectional view showing another embodiment of the semiconductor laser according to the invention. Here, 1... n-type substrate, 2, 4, 2', 4'
......Clad 1.3,3'...Active layer, 5...Kya, P layer, 6.6'...p
Type diffusion layer, 7.7', 8...ohmi. electrode, 9... electrical insulating layer, A, B...
...It is a diode. Electrical insulation layer $/111! I Hana 21! I

Claims (1)

[Claims] The present invention is characterized in that a diode electrically independent from the diode portion including the light emitting portion is formed in the same element, and the latter diode enables the thermal resistance of the element to be measured.