Design and performance of semiconductor microstrip laser

A novel semiconductor laser, the microstrip laser, in which the laser epi film sits on a thick gold ground plane rather than on a conventional semiconductor substrate was invented and demonstrated. The microstrip laser possesses advantages for high frequency and high power operation, because the microwave propagation properties of the microstrip laser are better than the conventional laser, and the thermal resistance is lower.;Microstrip lasers were fabricated in the InP/InGaAsP system by a gold bonding and substrate removal technique. The lasers emit light at 1.55 mum wavelength. Narrow ridge microstrip lasers showed threshold and efficiency performance comparable to conventional lasers. Because of the fabrication technique which inverts the grown epi, the lasers were all n-ridge lasers, with ridges etched through the active region to prevent lateral leakage current and high thresholds.;Microstrip lasers appear to be more susceptible to the opening of parasitic leakage current paths than are conventional lasers. This limited the ultimate performance of the low threshold microstrip lasers discussed above.;Experimental results on devices in which the SCH and active region had not been etched away show that the thermal resistance of the microstrip laser can be more than 3 times smaller than a conventional laser at room temperature. However, because these devices had high thresholds and low efficiencies they did not demonstrate high power operation despite the excellent thermal resistance.;The microwave propagation properties of the microstrip laser are also much improved relative to a conventional laser on a doped substrate, with the microwave loss being a factor of two smaller, and the phase velocity being more than twice as high. These improved propagation properties ensure more uniform microwave current injection to the laser, and better optical response at high frequency.;The microwave propagation properties are important, because as is shown in this dissertation, at high frequency significant phase delays are present along the electrode length. Because of this, the laser behaves as a distributed electrical element rather than a lumped element as has been traditionally assumed, and the nature of high frequency current injection is modified. In conventional lasers on doped substrates, high frequency current is highly localized within the vicinity of the feed point, and the effect worsens as the frequency increases. This causes current rolloff that limits the bandwidth to about 30 GHz in doped substrate lasers. In the microstrip laser, the bandwidth limits do not become manifest until frequencies greater than 50 GHz are reached.