M. Zimprich

Laser operation of Ga(NAsP) lattice-matched to (001) silicon substrate

The lattice-matched growth of the direct band gap material Ga(NAsP) is a seminal concept for the monolithic integration of III/V laser on a silicon substrate. Here, we report on the growth, characterization, and lasing properties of Ga(NAsP)/(BGa)(AsP) multi quantum well heterostructures embedded in (BGa)P cladding layers which were deposited on an exactly oriented (001) Si substrate. Structural investigations confirm a high crystal quality without any indication for misfit or threading dislocation formation. Laser operation between 800 nm and 900 nm of these broad area device structures was achieved under optical pumping as well as electrical injection for temperatures up to 150 K. This “proof of principle” points to the enormous potential of Ga(NAsP) as an optical complement to Si microelectronics.

Band structure properties of novel BxGa1−xP alloys for silicon integration

We have grown and investigated the band-structure properties of novel III-V alloys based upon BxGa1−xP. These layers are utilized as strain-compensating layers for the lattice-matched integration of novel direct bandgap Ga(NAsP) quantum well lasers on silicon. Experimental and theoretical studies reveal the dependence of the direct and indirect band gaps for strained BxGa1−xP layers grown on silicon as a function of Boron composition from which we derive the properties of free-standing BxGa1−xP. For Boron fractions up to 6%, we find that the bowing parameter for the lowest (indirect) band gap is − 6.2 ± 0.2 eV. High crystalline quality and promising optical material properties are demonstrated and applied to monolithically integrated Ga(NAsP)/(BGa)P multi-quantum well heterostructures on (001) silicon substrates. Our results show that novel (BGa)P layers are suitable for strain compensation purposes, which pave the way towards a commercial solution for the monolithic integration of long term stable laser ...

High room-temperature optical gain in Ga(NAsP)/Si heterostructures

We analyze the modal gain of Ga(NAsP) multi quantum-well heterostructures pseudomorphically grown on (001) silicon substrate by metal-organic vapor-phase epitaxy. Using the variable stripe length method, we obtain high modal gain values up to 78 cm−1 at room temperature that are comparable to the values of common high quality III-V laser material. We find good agreement between experimental results and theoretically calculated gain spectra obtained using a microscopic model. The results underline the high potential of Ga(NAsP) as an active material for directly electrically pumped lasers on silicon substrate.

Correlation of the nanostructure with optoelectronic properties during rapid thermal annealing of Ga(NAsP) quantum wells grown on Si(001) substrates

Ga(NAsP) quantum wells grown pseudomorphically on Si substrate are promising candidates for optically active light sources in future optoelectronically integrated circuits on Si substrates. As the material is typically grown at low temperatures, it has to be thermally annealed after growth to remove defects and optimize optoelectronic properties. Here we show by quantitative transmission electron microscopy that two different kinds of structural development are associated with the annealing. First of all, the quantum well homogeneity improves with increasing annealing temperature. For annealing temperatures above 925 °C the composition becomes less homogeneous again. Second, voids form in the quantum well for annealing temperatures above 850 °C. Their density and size increase continuously with increasing annealing temperature. These results are correlated to the optical properties of the samples, where we find from temperature-dependent photoluminescence measurements two scales of disorder, which show th...

Efficiency-limiting processes in Ga(NAsP)/GaP quantum well lasers

We report on the carrier recombination mechanisms in dilute nitride Ga(NAsP)/GaP quantum well lasers. Spontaneous emission measurements show that defect-related recombination in the devices is less significant compared with other GaAs-based dilute nitride lasers. From temperature dependent measurements, we find that the threshold current density, Jth is dominated by non-radiative recombination process(es), which account for at least 91% of Jth at room temperature. The characteristic temperature, T0 (T1) is measured to be ∼104 K (∼99 K) around 200 K, which drops to ∼58 K ( ∼37 K) around room temperature. Hydrostatic pressure measurements reveal a strong increase of threshold current with increasing pressure. This implies that current leakage dominates carrier recombination which is also responsible for their low T0 and T1 values at room temperature.

MOVPE growth and characterization of Ga(NAsP) laser structures monolithically integrated on Si (001) substrates

Laser structures containing the dilute nitride material Ga(NAsP) can be grown lattice matched on silicon substrates with high crystal quality and low defect density. Lasing operation from broad area lasers up to 120K is verified.

Band structure properties of (BGa)P semiconductors for lattice matched integration on (001) silicon

We report the band structure properties of (BGa)P layers grown on silicon substrate using metal-organic vapour-phase epitaxy. Using surface photo-voltage spectroscopy we find that both the direct and indirect band gaps of (BGa)P alloys (strained and unstrained) decrease with Boron content. Our experimental results suggest that the band gap of (BGa)P layers up to 6% Boron is large and suitable to be used as cladding and contact layers in GaP-based quantum well heterostructures on silicon substrates.

Physical properties of monolithically integrated Ga(NAsP)/(BGa)P QW lasers on silicon

This paper reports the lattice matched monolithic integration of novel direct band-gap dilute nitride Ga(NAsP) QW lasers on an (001) silicon substrate using novel (BGa)P strain compensating layer. Lasing operation up to 165K is verified with a threshold current density of 1.6kAcm−2 and a characteristic temperature of 73K for a SQW device, which is a positive step towards a commercial solution for the monolithic integration of long term stable laser diodes on silicon substrates.

High modal gain in Ga(NAsP)/(BGa)((As)P) heterostructures grown lattice matched on (001) silicon

We present modal gain measurements in Ga(NAsP) heterostructures pseudomorphically grown on silicon substrate. Using the variable stripe length method we analyze the modal gain performance of an unprocessed single quantum well sample for different excitation densities. We obtain high modal gain values up to 55 cm-1 at room temperature. These values are comparable to those of common high quality laser material. This demonstrates the high optical quality of the new dilute nitride material Ga(NAsP) and underlines its candidacy for electrically pumped lasing on silicon substrate.

Photoluminescence and optical gain of Ga(NAsP) heterostructures pseudomorphically grown on silicon (001) substrate

The novel metastable dilute nitride material Ga(NAsP) is a very promising candidate for electrically pumped lasers on silicon because it can be pseudomorphically grown on silicon substrate. Here we investigate the optical properties of a series of multi-quantum well Ga(NAsP) samples grown lattice matched on GaP and Si substrates. Temperature and excitation resolved photoluminescence spectroscopy indicates a significant impact of disorder-induced carrier localization effects on the optical properties. On the other hand, optical gain measurements reveal high modal gain up to 80 cm−1 at room temperature and demonstrate the suitability of this new material as an active material for laser devices. A comparative analysis of optical gain and photoluminescence data demonstrates a strong impact of the barrier-growth conditions on the optical quality of the material.