Temperature performance of the edge emitting transistor laser

Abstract

The characteristic temperature (T0) of the edge emitting transistor laser (TL) is studied numerically. For the deep-ridge TL, the common base (CB) mode characteristic temperature (T0,CB) is a lot lower than the common emitter (CE) mode characteristic temperature (T0,CE), which is comparable to a conventional laser. This is resulted from the increase of the emitter to base current gain with the base current, which amplifies the increase of the CB threshold current with temperature. For the shallow-ridge TL, the T0,CE is found to be also rather low and is only slightly higher than the T0,CB. This can be attributed to the large fraction of electron current in the total base current, which is related to the large thickness of base layer and the insertion of quantum wells in the TL.

Doping of Active Region in Long Wavelength InP-Based Transistor Lasers

“…The decrease of the slope efficiency of TLs with the increase of the doping level in the MQWs can be first attributed to the electron current in the base current of a TL, which does not contribute to the laser output [16]. As shown in Fig.…”

High current gain transistor laser

“…Under the same BE bias voltage, the number of electrons injected from the emitter into the base increases noticeably relative to the case of deep ridge TL, leading to the increase of the current gain. As more electrons are present in the base region, more of them diffuse to the base contact, increasing the portion of electron current in the total base current 11 . Because the electron current does not contribute to the laser emission, the slope efficiency of the a-TL is lower than that of the deep ridge TL and is varied with the base current as shown in Fig.…”

“…1 , the MQWs are placed above the p-doped base layer. Thus both the diffusion of p-type dopant (Zn is usually used for InP material system) into the MQWs and the optical absorption of the p-type base material can be reduced, helping to improve the optical properties of the device 11 . Only a simple two step epitaxy process is needed to fabricate a-TLs.…”

“…Thus a base layer having as small as one to several tens of nanometer thickness, which is essential for ultra high speed operation of transistors, can be adopted. However, it is difficult to have a base layer this thin for other kinds of TLs, because of constrains from either the structure of the base layer for a shallow ridge TL 2 or from the fabrication process of a deep ridge TL 11 . Finally, it is worth noting that though the device structure studied in this work is ridge waveguide npn-type, the proposed structure can be used in other types of TL such as pnp TLs and vertical cavity TLs 17 .…”

“…The majority of the electrons are consumed by stimulated light emissions, leading to a current gain which is a lot lower than the gain of a traditional transistor. The common emitter (CE) mode current gain (collector current/base current) is lower than 5 for most, if not all, of the TLs studied, either experimentally 1 2 3 6 7 8 9 10 or numerically 11 12 13 . The low current gain may limit the performance of systems that use TLs.…”