U.S. Philips Corporation

Hubertus P Ambrosius

Adriaan Valster

Carolus J Van Der Poel

Jan Opschoor

Helena J Boerrigter-Lammers

Radiation-emitting semiconductor diodes are used as laser diodes or LEDs inter alia in optical disc systems, laser printers and bar code readers. The emission wavelength in these cases lies preferably in the visible range of the spectrum. Known diodes have an active layer (3A) and cladding layers (2, 4) which comprise either AlGaAs or InAlGaP. These known diodes have the disadvantage that they do not cover a portion of the visible spectrum between 880 and 600 nm. A diode according to the invention is characterized in that the active layer (3A) comprises Al.sub.x Ga.sub.l-x As and the cladding layers (2, 4) comprise Al.sub.y Ga.sub.w In.sub.l-y-w P, while the active layer (3A) has such an aluminjure content (x) and such a thickness (d) that the wavelength of the photoluminescence emission lies between approximately 770 and 690 nm. This results in the availability of (laser) diodes covering the entire spectrum from approximately 880 nm to 600 nm which operate satisfactorily, supply a high power, and are easy to manufacture. Preferably, the active layer comprises a (multiple) quantum well structure of alternating quantum well layers and barrier layers, both comprising AlGaAs, but with different aluminium contents.

Radiation-emitting semiconductor diode and method of manufacturing same

A method of manufacturing a semiconductor device, such as a semiconductor diode laser, is set forth to form a mesa and current blocking structure on either side of the mesa. In this technique a lift-off step is used to form a contact layer as a direct result of removing semiconductor layers. This is accomplished by using a selective etchant that removes overlying layers, but does not remove a subjacent layer which may be the contact layer. As a result, the growing process is economized by an inexpensive method having a high yield.

Method of manufacturing a semiconductor device comprising a mesa

Semiconductor diode lasers of the so-called NAM (Non-Absorbing Mirror) type are used due to the high emanating power as writing (and reading) lasers in optical recording systems. The known lasers of this type include both in the active region (13') and in the mirror region (17, 19) a cladding layer (1), which fills a groove and is provided on an absorbing layer (9) (17, 19). The fundamental lateral mode is favored in both regions (13'), (17, 19) by absorption of part of the radiation produced. Due to the absorption in the mirror region (17, 19) mirror degradation occurs, which limits the maximum power and the life of the laser. A new semiconductor diode laser includes in the mirror region (17, 19) a first cladding layer (1'), a radiation-guiding layer (2') and a third cladding layer (6). In the radiation-guiding layer (2'), a radiation guide (15) is formed by an arrangement (12) in the radiation-guiding layer (2'), by which a step is formed in the effective refractive index. Further, the layers (1', 2', 6), which are located in the amplification profile of the radiation guide (15), have a larger band gap than the active layer (3). Due to the particular structure employed, no absorption of radiation occurs in the mirror region (17, 19). As a result, the occurrence of mirror degradation is limited so that lasers are obtained having a high power available and a long life.

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Eindhoven, Netherlands

Hubertus P Ambrosius